I'm DMing a group right now in Eberron (so I already have to take Action Points into account for encounter design), and my players, who are fairly new, are super intrigued by all of the interesting feats they have to choose from (they have PHB, Eberron and the Complete line of books to choose from). In an effort to give them more interesting choices at levels up, I've decided to speed up their feat progression somewhat. They now gain a new feat every other level.
Now, I've done the math, and that means they'll have one feat more than they normally would at level 5, and from levels 7-10. Which means for half of the levels from 1-10, they have the same number of feats they normally would, and for the other half, they're essentially no better off than humans (none of them are playing humans).
Do I even need to bother re-balancing encounters until the number of extra feats gets much higher? And how does one go about balancing encounters for characters with more feats than usual for their level? The only resource I've been able to find that even acknowledges the issue is E6, which just kind of shrugs its non-existent shoulders and basically says "I dunno, at some point bump up the ELs".
Does anyone have any experience with that system, or experience being an equally foolishly gregarious DM, that can shed light on how this feat progression impacts balance at mid to higher levels?