Every class really. Sometimes I get bored and jump to another just because I can. I'd rank my taste in classes like this: 1. Soldier 2. Pyro 3. Engineer 4. Scout 5. Heavy 6. Medic 7. Spy 8. Sniper 9. Demoman
Depends on what you mean by "it sucks", does it mean it's 3-4 score material? Highly unlikely. For some people if this game ends up a 8 overall score then it will be considered a flop, the hype meter has skyrocketed. I don't think it's gonna "suck", even if it's not what everybody expected.