I find the challenges are like having to get 10 extra trophies per level. All the requirements read like trophy requirements.I've earned a lot of trophies in Blops 2, and once I get intel(two more missions) and challenges out of the way I'll only have zombies left. Sadly, the "Tower of Babble" trophy looks damn near impossible. I might be able to get some friends together and go for it, but I doubt it.
Since this is the first game with online trophies. This is also the first time I've played a COD online...it's not very fun. I prefer the modes in Battlefield or Medal of Honor over the COD ones. I cannot find anywhere that tracks my Combat Training wins either. You need 10 for one of the trophies.
How difficult is Crushing? I want to play through it again, but I have other games waiting around for me, including U: GA.
If you have finished any of the other ones on Crushing you won't have a problem with this one. No really annoying end boss makes it easier too.