I might be up for this. Love the first game, but it's getting released right around the time I might be making a trip. I'll EVENTUALLY be getting this, but possibly not at launch.
It's also a bit less like Left 4 Dead now. It's still 4 player with a heavy emphasis on co-op, but now there are more jobs to do, with some jobs taking course over a number of days. It's even possible that you'll get unlucky and have the cops trailing you between jobs, forcing you to ditch your van for another ride. They also give you a lot more freedom on HOW a job is done. In the original Payday, stealth wasn't very much of an option... but in Payday 2 it is possible to do some jobs without ever alerting the cops to your presence.
You also can't max out every class in this one. You can get up to 120 points to spent on talents to make you better and you can spread those out however you like.
Heres a skills calculator if you want to look at what you can do. Some skills make your weapons better or give you new tools (like a turret or c4 to blow open safes). Other skills give you useful abilities like the ability to not have bags slow you down as much or to become so persuasive that you can make enemies fight for you or make civilians have a chance that they'll revive you if you shout at them. It's a lot of cool stuff.
There are also a TON more masks this time around and you earn them and weapons by completing a full a job. At the end of a full job is a "payday", where you pick from one of three cards to get a reward (on top of the money you've already received). Rewards can be guns, gun mods, mask designs, paints, materials for the masks, and logos for the masks. Some masks are rarer than others (the J.D. Dillinger mask is something like a 1/1.5 million chance).