Someone care to summarize the differences between 3e version and the 3.5 revision of the D&D rules?  I'm familiar with 3e, but I've had pretty much no experience with 3.5 except for an extremely casual glance through the PHB once in a store.

I ask primarily because I recently purchased Iron Heroes, which states that it incorporates the revisions from 3.5.  I'm not terribly inclined to purchase the core rules all over again, particularly without knowing anything about them.

Go here and download the 3.5 update booklet WotC made.

Well, as Iron Heroes already has the differences incorporated, why would you have to buy the D&D books again? IH is pretty complete.

They changed the classes quite a lot, making the Ranger and Bard actually usable.The Paladin got a Pokemount (summoned out of thin air), the Barbarian got some dead levels filled, etc.

Some feats were changed. Power Attack now gets you 2 points of damage for every single point of BAB sacrificed. Spell Focus increases your saving throw by a measly point.

Most of the changes were done to the spells. IMHO not badly, but if you come at me saying the words "shadowy illumination", I just have to strangle you with a CAT5 cable...

In other words: Not neccesary, but a decent revision. Definitely no need to buy it to support a completely different D20 game.

I'm having trouble coming up with any critical problems that would arise from support an IH game with the 3.0 PHB.  The changes from one edition to the next were largely in things that don't apply in Iron Heroes.

The update booklet I linked to above goes over the changes between the editions in some detail.

I didn't figure there would be enough differences that would come up in playing during Iron Heroes that I'd need to pick up the 3.5 rules, but I thought I wouldn't make that assumption without asking first.