There has been a great deal of discussion about the new rule on the Pinnacle forums, especially on the "official" thread that includes commentary from Clint Black, who gives official rulings for Savage Worlds. As the face of Pinnacle on this, he has a lot of insight on what the rationale for the change was and what the impacts are.
First off, what was wrong with the old rule?
Short Answer: It created some unintended consequences and made players spend too many Bennies just to act. The new rule makes things faster, frees up more Bennies for more interesting things, and better fits the "up, down, and off the board" mantra.
There was an underlying issue nagging at us we finally realized. Players were spending a disproportionate number of Bennies to simply act as opposed to spending them to do cool stuff.
Changing this one rule fixed all those issues and made the game even better in other ways as well such as the faster resolution of Shaken results for every single character in any combat. (Source)
It may not seem like much, but with only two results for recovering from Shaken instead of three, resolution is sped up dramatically. And by making recovery with actions easier, players don't have to spend as many Bennies just to take an action and can instead spend them to make those actions awesome! Finally, we realized the three conditions for Extras, Up, Down, and Off the Board, had really been four with the inclusion of "Up... but recovered without a raise and can't act." It's a temporary condition to be sure, but one that occurs regularly. GMs never have to worry about that "floating" condition again. Extras who are Shaken can't act, and those who are not Shaken can–there's no middle ground. (Source)
Doesn't this diminish the value of Shaken?
Short Answer: It reduces the likelihood of a "stunlock" from Shaken, which was never meant to be the major benefit of the Shaken mechanic in the first place. The designers see this new rule change as a desirable improvement that takes away unintended consequences.
Well, in one way it really can't "diminish" it's effect since it affects all characters equally. What it can do is change the dynamic, but even then, really not so much as it may appear [...]
I think the disconnect here is the belief that the major benefit of Shaken is to prevent characters from taking actions.
Think about that for a moment. That would mean that the primary point of the mechanic was specifically to extend and drag out combat by negating actions on both sides of a conflict.
I can tell you that was never the ultimate goal of the Shaken mechanic.
But that is what happened, so it's no surprise folks think that.
Yeah, it will change the dynamic somewhat but we think you'll discover the change is dynamic itself. (Source)
How does this affect Tricks and Tests of Will?
Short Answer: The primary effects from Tricks and Tests of Will (-2 Parry, +2 to next action) are completely unchanged. It is only less powerful if your primary goal for it was to get a raise in order to make your opponent Shaken and therefore create a "stunlock", which as written above, was never really a design goal or desirable behavior.
As far as characters with a "niche" of only causing Shaken, most of their effects didn't change as making a target easier to wound through Shaken is completely unaffected by the rule, which really is where timing and coordinating come in. [...]
With Tricks and Tests of Will, the effect was actually even less since the primary effect of each from a success, -2 Parry or +2 to the next action, is also completely unaffected by the rule. It takes rolling 4 points higher than the target (which a d10 Wild Card only does 50% of the time over a d4 Extra) to cause a Shaken and it would only really come up against a foe who can't be targeted to benefit from the damage effect of Shaken.
That of course means Tricks were even farther down on the affected scale than Tests of Will since their primary effect is only useful if the foe can be targeted, so the idea of using a Trick where it had to get a raise to be effective at all almost never came up, much less as a repeated tactic or niche of any character. (Source)
What impact does this have with +2 bonuses to Shaken (Combat Reflexes, Undead, etc.)?
Short Answer: When you run the numbers, a +2 bonus to recover from Shaken increases your odds by less than half of what it did under the old rule.
The worry is this makes a +2 to recover from Shaken more powerful because the chance of recovery is so high.
The misconception there is comparing the old odds of acting to the new odds where to truly determine the change in power, the comparison should be from the old effectiveness of the ability vs. the new.
For example, a d4 Spirit Extra without +2 had a 6.25% chance of recovering with an action by the old rule and a 25% chance with the new one. With the +2, they had an 18.75% chance and now a 75% chance. Both of those increase success by exactly the same amount, three times.
So the effectiveness of the ability is exactly the same. It triples the chance of recovering for a d4 Spirit Extra.
But get to a d8 Spirit Extra. The odds without +2 are 12.5% and 62.5% respectively. With the +2, the odds are 37.5% and 87.5%. Meaning the old rule also tripled the chance of recovery for a d8, but the new rule increases the chance of recover by only 1.4x.
So by the new rule, that +2 to recover is actually less than half as effective as it was using the old rule. It makes it less powerful not more. (Source)
Regarding whether the rule change makes Combat Reflexes overpowered:
Nope, it really doesn't. Nor does it make it worthless (another concern others have had). (Source)
Other players have pointed out that it is still very useful when your character has penalties from Wounds or Fatigue, putting the Edge about on par with Nerves of Steel.
Does this rule favor Extras over Wild Cards?
Short Answer: Even when Extras have a +2 bonus to recover from Shaken, Wild Cards are better off with this rule.
One of the concerns noted is the belief this change favors Extras, particularly those with Undead or some other ability granting a bonus to recover from Shaken.
I know it's hard to simply accept our word that doesn't happen, so I thought perhaps some evidence from an unbiased source... Zadmar's combat simulator.
[Lots of numbers get thrown out from the simulation]
While not quite as big a difference as with the living goblins, the Wild Card once again won significantly more fights on average under the new rule than the Extras, even though they now have Undead with +2 to recover from Shaken. (Source)
I'm Still Not Sure About This Rule...
This has been playtested for around a year now in multiple games all over the world, and it works just fine. (Source)
We've been playtesting this for a while specifically because it felt like it could have serious repercussions but the results came back overwhelmingly positive. We can only say the same thing we've said about other aspects of the system, "Try it out for a while."
And if it still doesn't work for a particular group, then they can always use the old rule. There are still folks who use +2 damage per raise [last seen in Savage Worlds Revised] and we haven't broken down their doors to take away their dice...yet. ;) (Source)
I don't trust this Clint guy, I want to hear from someone on RPG Stack Exchange!
Short Answer: I have run the rule for the last several weeks in my weekly game and I can affirm that the rule does work and tends to make combats faster and easier to GM. While there was a lot of skepticism about the rule, my players have all come to very much love it.
There were definitely some changes in tactics. If a character Shakes an enemy, they can no longer rely on the enemy being likely to be out of commission for a round. This means that there is more pressure to "press the advantage" by trying to get a second Shaken result to wound the enemy, or to roll high in the first place.
Two of my players did decide to swap out "Combat Reflexes" though because they felt that it was no longer a "must have" Edge, but they still saw it as a useful Edge on par with others like Nerves of Steel. To me, that's not really a design flaw as much as an improvement.
There was concern that it weakened Tricks, Tests of Wills, and Shaken-dealing powers (e.g. Stun), but really what this meant was that the players had to improve their tactics and actually work together because they could no longer rely on a single PC taking an enemy out of commission for at least a turn (or forcing them to spend a Benny). Interestingly, players have been more likely to use Tests of Will and such in order to make it more likely that their teammates will roll well in order to get the wound.
We did fight undead once (getting the usual +2 vs Shaken) and it actually made the fight better. Instead of having undead just milling around unable to act after a glancing gunshot, they instead were able to recover quickly and continue advancing on the party. This made them more threatening, better matched players expectations of an ever-advancing horde, and generally made the game more fun to play.
All in all, I can corroborate what Clint says and it seems that, although there are definitely concerns on paper, it tends to work out well at the game table. Definitely give it a try and you may come to like it as my players and I have.