I played 3E quite a bit- it was responsible for getting me back into D&D, after a long hiatus! It also elevated my DMing skills quite a bit.
Overall, I very much enjoyed it. Also invested a ton of money into buying stuff for it, lol. (I will NEVER run out of new adventures to run, or new monsters or ideas to bring) It was my favorite iteration of the game so far.
Some likes:
-Blew the doors wide open on character creation! Some classic classes returned, Sorcerers added, more racial options. Arbitrary limits eliminated! And done so elegantly too- lets just make humans cooler, and we won't HAVE to limit the others! Multi-classing now available to all, and with more options. Feats added. Prestige classes added.
AND:
They actually made clerics cool! No more cookie cutter battle medics that double as "undead begone!". You had real choices to make your cleric your own. Loved the idea of domains! Spontaneous casting meant you could actually prepare spells OTHER than cure x wounds, as a matter of course lol.
- Spell casters. No more "one pump chump" low level casters. 0 level spells now actually added something to the game. A new alternate take on arcane casters in the Sorcerer. More cohesive system for partial casters. And plenty of new (to me anyway) spells.
-D20 system. tied all the disparate systems together in a simple, straitforward way.
-OGL. Nice- open it up to other publishers to make content for the game.
Modules/adventures. The official adventures published by WoTC stepped it up a few notches. There were some real classics!
Some dislikes:
- crunchy!! If you don't use minis, be ready for long, drawn out combats with plenty of confusion and rules arguments...
-power creep. The power level of even a newbie party was considerably higher than in previous editions- requiring much more difficult encounters to keep up the challenge level. Which, in turn, accelerated the rate at which XP was earned. This actually became a fun challenge for me- amping up adventures to challenge my players, without handing out xp and loot like it was candy.
- the "look" The new dungeonpunk aesthetic was not for me.
I'd still play it today, if a game were offered or someone wanted me to run one.
I'm really likin a lot of what they did with 5th ed, though, and would prefer to play that.