Yes BC2 is definitely worth it. Prone isnt a big deal, i say that prone promotes camping and EA is trying really hard to make this less n00bish than MW/MW2. Leaning isnt necessary either imo. The campaign has an incredibly interesting story with plenty of cut scenes to keep you interested and keep the story behind the game very strong.
Next, Specs/perks, there are 3 slots for specs and in each slot you can select only one that you want to use. you need to unlock different specs by using that item or class (ex: smoke grnd launcher by using grenade launcher & shotgun upgrade by using shotguns).
Each upgrade does a certain thing, like the shotgun upgrade, gives you a larger capacity for SG ammo, things like that.