I was luky enough to get hold of this on the launch day and so was very very disappointed to fun the public multiplayer facility was bugged. BUT, that has now been fixed and I'm enjoying what has to be one of the best all time multiplayer games ever designed!
This game has specifically been designed with co op gaming in mind, and only that in mind really. I must say that the solo mode is very poor as the AI on your team is useless and the cops aren't all that smart either. But the game comes alive when you throw in other human players.
As a game, you have easy and hard jobs that you can either shoot your way thru or map out a perfect hit and walk away silently with (literally) bags of money. Then throw in that your best mates are also running along next to you but acid stably shoot someone at the wrong moment, then the gaming in begins. All hell breaks loose an you get to shout at your mate down your mic because now you have a dozen cops swarming all over your nicely planned bank heist that was going to earn you money for your next weapon upgrade.
So, weapons. Yep ou have to buy them, but you also get to unlock a whole host of add-ons that allow them to be pretty unique within the game. You also have that option with masks too.
I would say that after playing the game for a couple of weeks, the game doesn't have a huge shelf life at present due to there being limited levels for higher level players, but future DLC should hopefully bump its life along a little further. It is a game that can offer a group of mates plenty of fun for a good while though, so I you have mates to play with, then it's a must.