In Black Ops, for the first time ever, i actually noticed and really liked the pro perk system. For those who cant remember/didnt play it. Black Ops had a system where you would have to complete 3 challenges using a perk to unlock the pro version. For example to unlock hardened pro I think you had to shoot 200 bullets at air support, kill x number of people through a wall and something else I cant remember.
In my opinion this system worked really well for 2 reasons.
1. They could use the challenges to direct players to use the perk in a different way than they would naturally. For example challenges with an objective nature forces the player to actually try and cap flags, or plant bombs. In demolition I would normally hang back for a while, but after trying to get the flak jacket pro I was always planting. I could have both bombs planted within a few minutes sometimes. This makes the game more enjoyable for everyone because the objective matches are now focussed on the actual objective, not just another team death match.
2. You felt like you earnt the pro perk and really noticed its benefits. For example the tactical mask pro perk was so hard to unlock, you had to stun 30 people and then kill them, and do the same for flash bangs and nova gas. Thats hard! and getting it taught me the benefit of using the tactical grenades. But when i unlocked it, I felt like I'd achieved something, and I appreciated the pro bonus of not being flashbanged
In essence, "pro" perks. were only unlocked after you became a "pro" with the perk.
Now MW3, if im not mistaken you just unlock pro versions after using the perk for a bit. I dont even know how to see the challenge, it just unlocks after a bit. The pro perks are not really pro anymore, just "well you used this alot, well done, have a bonus" perks. And im my eyes, thats a shame, because i really liked the black ops system.