My first RPG was D&D 3.0, tried it at the start of college. Was hooked on pen & paper RPGs immediately, tons of fun when you put in some story, character, and drama into it. Branched out from there to different rpg's, usually ones with that were more story-oriented, rather than a tactical action focus like D&D. My room mates and friends all joined in for many different games over the years, and it never ever got old.
I got to try 4th edition briefly. We all had our reservations, but after trying it out, I think it's better. Things are more streamlined, which I had feared would be a detriment, but it turned out to be a good thing. D&D is a very simple game, as RPGs go, so it makes sense that it should be further refined as a simple, easy to pick up RPG, good for newbies, and good for fast action.
Although the 'roles' (tank, controller, striker, etc) were a bit jarring, it really does make sense - characters tended to fall into those duties before, even if it was unspoken, or we didn't call them that. I also appreciate how it served to focus each player's attention on their specific over-lying goals within the team. D&D was always very tactical, and by clarifying in this way, it becomes a little bit more like a 'sport,' for lack of a better description. The vagaries and ambiguities and pretenses are washed away. I don't normally want that in my RPG's, as I love the story, drama, characters, possibilities, etc, but in D&D's case, I find it to be a well-fitting niche. If I wanted a story-oriented RPG, I'll play something else. If I want tactical fantasy action, it's D&D, baby. So although it's a sorta drastic change in perspective, I think it's for the better. It allows the D&D system to focus on what it's good at, and not bother so much with what it's not so good at.
I also like that, rather than risking dying to a lvl 1 orc at character creation, instead you risk dying to a horde of those orcs. Feels much more heroic. lvl 1 in prior editions, you weren't a hero; You were a chump with a sword. Well, no longer!
That said, most my time has been spent with more story oriented RPG's. I've tried dozens of different settings and systems with my friends, but the one that keeps sucking us back is EXALTED. Exalted is incredible. Few settings are so epic and ripe with possibility. And who doesn't want to play a crazy, sexy, cool demigod with earth-shattering kung-fu that could save or destroy the entire world..... at char-gen?
Unfortunately, system-wise, it's the direct opposite of D&D. Crazy complex and cumbersome, wrought with subtle problems that are hard to pick up on at first. But the character customization..... It absolutely pees all over D&D on that front. After having made and played many characters for Exalted, you won't see me crying about the removal of multi-classing in D&D. It's silly by comparison.
I no longer play RPGs with my friends, we've gone in our different directions. But since Google Wave, I've picked up Exalted again. Wave is a great tool, works better than instant messengers, or messageboard.
Some day I'd like to have another good, long campaign of D&D 4. If I get the chance I'd like to finally try my hand at DMing it.