Yup, Newb here, only playing since F2P
Favourites:
Engineer - By far, highest ranking in playtime. Earlier in this thread, if I remember correctly, I was ninja'd by someone saying how, since you're not good in Twitch, you have to employ something of a "lateral thinking" to be good in those games, and the engineer offers nice opportunities for those strategies. And it is not really boring, thanks to Spies. And really, thank you Spies. It's nice fighting you. Speaking of which...
the Spy - Remember that "Newb" in the beginning? I suck at the Spy and I don't play him too often, but he is an exciting and rewarding class. Plus I once - somehow - set my record for most points in a life with him. And I believe it's a respectable number. Which I won't tell, because you could crush my illusions.
Heavy - Initially, Heavy was the only class to pick when I felt completely useless otherwise. But I've grown to like him. Seems to be extremely straightforward, but being The Tank makes it kinda interesting.
Meh, in order of liking:
Sniper - I
do like the role, in general, and here specifically the character, but I'm not good enough to enjoy him. My Most kills resulted from spamming arrows in the general direction of the enemy (with one shot of truly awesome marksmanship

. Also: map knowledge. Also: there is always one other sniper, mostly two, and I don't think that I'd contribute anything. I really only play him in a Payload Defense or Dustbowl Attack/Defense.
Pyro - now, I don't like the role. One of my least played classes. But this statement is very subject to change, because I plan to play him more often. Being a good, effectively ambushing Pyro who knows how and when to use an airblast might be something that I should train. Seems like fun.
zeh Medic - Not a class that I'd pick deliberately, but I don't mind playing him when the team needs one. Being directly responsible for making an important push is nice. well... (in case the Heavies are playing along - yes, I'm referring to you bulletproof guys who refused to take out a sentry three times which killed us by the dozen, 12 meters away from the final checkpoint). It's just that in the moments in between, when I run into an enemy, I feel impaired.
Soldier - When there's no need for any of the above and I don't feel like adding any of the above to a round and I don't feel like going Heavy, Soldier's the class to pick. Cause mayhem. Could be fun, but - turns out - a rocketlauncher is just not my weapon of choice.
Scout - Likewise, ranks equally to the soldier: Could be fun, but! ..is mostly about Twitch. More interesting than the soldier, though. I want to work on this one.
Hate
Spammoman - also known as Reloadman. Plus: the most irritating opponent for me as an engineer.