While we have a question about the differences between Star Wars d20 Revised and Saga Editions, I'm wondering what the differences are between the original version and the Revised version. Furthermore, do any of these differences prevent content from one being used in the other? They seem pretty similar to me.
Mechanics-wise, there were a number of changes, mostly small. several new species were added, and a couple were redefined. There was the addition of the Tech Specialist class, very similar to the Artificer class from Eberron. Most of the other changes were altered in some small way, and better balanced. A couple of skills were added, and the Force Skill descriptions were no longer kept separate. The same with feats - several new ones, a couple of small changes to older feats, and the Force feats in with the rest, rather than separate.
One of the larger mechanical changes was that armour changed to DR instead of improving your Defense. However, the DR only applied vs Wound damage, not Vitality. Another large change was that Attacks of Opportunity were added back into the system.
The vehicle and starship combat rules became more like the regular combat rules, using a grid rather than abstract ranges. Maneuvers were added, but the basics stayed the same.
Fluff-wise, there were a ton of changes - this book was published around the time of Attack of the Clones, and adds stills and flavour from that movie. Most of the characters had their stats updated to this episode, although a number of prior versions or older characters were also removed.
The most glaring removal was the sample adventure.
Sadly, I never had the chance to play this version, so can't contrast based on in-game experience.
I would say that material written for the original version would translate quite easily to Revised. Material created specifically for Revised would probably mostly translate, but anything to do with Attacks of Opportunity or grid-based vehicle combat, or armour, would need more attention.