I've been mostly DM'ing, so haven't had much chance to actually play my own character until recently.
Currently I am playing an elf predator druid. I really like the huge mobility (I can charge 16 squares) and have found good use for some of the control powers. Faerie Fire (lvl 1 daily) is very nice, and I stopped a runner with Cull the Herd (pull 3 squares). When I first read the class I felt kind of meh about the shapeshifting, but in play it's been fun. I do wonder if I should swap out one of my at-wills for a more caster-flavored one, but we'll see. I'm planning on taking Sneak of Shadows for some rogue goodies (and to have a party member trained in Thievery).
Classes that sound fun to play:
1) Cleric - I am eagerly awaiting Divine Power, but I'd happily play one without it
2) Swordmage - I've been a sucker for the gish since 1E, when they were just elven fighter/magic-users (or just elf for the real old-school)
3) Fighter - Many solid options and the first time playing a straight fighter appealed to me
4) Invoker - Great flavor, wrath of the gods stuff
5) Rogue - finally what they should have been
6) Bard - full of win
7) Avenger - it's a fun concept, but I am not sure how it would play out
8) Sorcerer - Several interesting builds, but chaos sounds entertaining
I agree with others who have said the Warden sounds pretty meh. Perhaps it plays better, but on an initial read it has weaker flavor than many other classes, and elicits a big shrug from me. Warlords and Shaman seem great in the hands of the tactically inclined player, but are not going to be easy to play effectively. Paladins have issues with being MAD, and their marks seem to not be quite as useful due to the limitation of engaging the foe every round.
All the V-build (having 2 different stats to-hit) classes (such as Paladins) have some problems and limitations. It's interesting that all the PH2 classes were A-build (relying on one to-hit stat). Certainly that lets you have far more powers to choose from because you can hit with any of your class powers effectively. You just may not get the best rider effects if you are lacking a bit in the secondary stat. More options = good.