Some things I like about 3.5
1. Rangers needed a boost, they got it. (possibly the worst 3.0 class)
2. Monks needed a boost, they got it. (and that stupid unarmed BAB thing had to go)
3. Bards needed a boost, they got it. (they've needed to be able to cast in armour for so long)
4. Spells like harm and haste needed to be nerfed, they were ridiculous. They were nerfed. And I might be alone in this, but I like the nerfs to buff durations. In 3.0 you might as well have just given everyone a +4 bonus on every stat, and not had to spend half an hour whenever a dispel comes into play.
5. Paladins getting more than one smite a day is good.
6. Some item costs were changed - boots of standard equipment getting more expensive and the skill boosting items likewise. These are good changes.
7. Greater weapon focus and specialisation are good because they give an incentive to stay with fighter longer - there needed to be some reason to stay beyond weapon spec.
8. The barbarian got a boost. I like the new version because he's a bit more differentiated from the fighter now.
Some comments on 3.5
The square facings didn't seem necessary to me, but there were things in 3.0 sizes that made no sense either. Look up the 3.0 dire tiger. It's the size of a bus!
The new weapon sizes do not confuse me. In fact, in 3.0 I used to be confused for a moment by the sizes of weapons wielded by giants. It seems a lot easier to me to refer to a huge creature with a huge greatsword than a huge creature with a gargantuan greatsword.
My gripes in 3.5
The divine casters, druids and clerics, are too powerful. They get second best everything - two good saves, D8 hitpoints, medium BAB... (okay, so skillpoints suck for the cleric) Then they get arguably the best set of spells in the game. Spells to heal themselves. Offensive spells like flamestrike. "Make me a fighter but better" spells like divine favour, divine power and righteous might. Tons of defensive spells like death ward, restoration, spell resistance. Proficient with heavy armour, and a decent selection of weapons. Wildshape.
Meanwhile, our poor old wizard has to make do with only one good save, D4 hitpoints, bad BAB AND no skillpoints! He's proficient with nothing, hasn't got armour proficiencies and can't wear it and cast spells even if he was to acquire the proficiencies! They can't heal themselves, their offensive spells have the unfortunate side effect of drawing attention to their frail, exposed bodies, and their defensive spells just don't stand up to divine ones.
Maybe if wizard spells were a lot more powerful than cleric/druid ones, their utter lack of any other redeeming features would be acceptable, but as it is it's just not.
My other gripe with D&D 3.5 is polymorph. I hate it. Someone takes an ECL race, but as soon as polymorph is around, everyone's a fire giant whenever there's a fight. What kind of fantasy book/film has it's main characters transforming into giants every two minutes? It's retarded. In my mind, the point of D&D is human-type heroes struggling valiantly against threats like dragons and giants and vampires and stuff like that using just their training and skills, not this polymorphing crap.