The TF2 unlock-ables and the class based achievements are both very well received. They are aptly named, and balanced to make them entertaining. Getting a new achievement feels good as it pops up in the right hand corner to congratulate you. The weapons can cleverly subvert the class and add new tactics, overall they are great!

The one problem everyone has is with linking the achievements to getting the unlock-ables. I was in this camp a while ago but now i see the reason behind that. They add extra incentive to them so you try new things. You realise from the medic achievements that you don’t have to die after each uber. Your greatest asset is healing people, others just go medic to get a uber charge. The Pyro and Heavy get a similar treatment, you learn new things about a class and become much more creative with it.

Its also faintly like an RPG except you just get different instead of better weapons, yet the achievements improve you as a class player.

I’m really anticipating the next wave of stuff.

EDIT – In response to Madlep’s comment I thought about having achievement’s tied to a medal system, to give rewards to those who are skillful with a class but a non significant bonus. Though the gear would need to be sorted first, and that would take a while to get 2 sets of gear which are fun to use. This might effectively expand the class choices subtly. This would make larger servers easier to find a niche to help your team.