UngeheuerLich
Legend
Thank you for filling in. Some feats wer huge: natural casting? The druid can now shapeshift and cast spells.I think that's actually fair to say. PF was designed with the idea that you could take any 3.5 material and use them in PF with a few tweaks - and that was generally true and with fewer than were necessary to go from 3.0 to 3.5, in my experience. I used quite a few 3.5 adventures with my PF game. I usually had to add a combat maneuver bonus and defense and very little else.
Now I think UngeheuerLich's list ends up overstating the individual effect of a lot of specific changes. For example, reworking some of the classes wasn't a huge problem - most of them could be ported between 3.0/3.5 with a little reworking - extra skill points, some different bonus proficiencies, etc. Same with the changes in skills and feats.
Bigger changes, in my mind, included changes to damage resistance, weapon sizing, and spell durations. Those made a pretty noticeable impact, particularly on the behavior of players.
But the big issue was just the broad scope of changes overall and I don't think any of the player or 3PP communities really expected how far they'd go or how many changes there would be. Cumulatively, it really made for a lot of little changes all over the place that made it harder to use cross-edition materials and utterly killed a lot of 3rd party 3.0 materials marketability. Also, quite a few of the changes seemed strongly related to an idiosyncratic vision of D&D that may have been held by a few of the WotC staffers at the time. So while I think some of the updates were absolutely worthwhile (updated bards and rangers in particular), I can totally see how a lot of people felt burned by the experience.
That was huge. But of course, I agree with your assessment about the amount of changes which had the biggest impact.
Also: The game became even more codified and less adaptable. And it went further away from its ADnD roots.