I've got this game on sale from the steam christmas specials, I have to say I'm really liking it.
the basic gameplay remains that of left for dead, with the twist that now you're robbing banks and doing stuff, engaging the law instead that the zombies.
but, while left for death was encouraging strategic, cooperative gameplay via killing you merciless if you didn't work as a team, payday has some mechanics that let the action flow better and the group act as a team even when everyone is a noob.
probably it's because the opposition now shoot, so you have time to take cover and fall back instead of being stranded and divided. probably because the police comes from less attack direction so you have a basic idea of what to expect next.
still, it works nicely and keeps the group close and the action flowing. there is a warning before enemy waves, so you have time to split up if there is a secondary objective to reach and to cancel if you did not manage to reach it.
I was actually surprised at how even new players (there was a stampede of gift reaching people on the servers) weren't doing anything stupid, given that playing l4d with seasoned friends resulted in frustration due to ramboes getting killed and wasting medpack and people barricading on ammo caches and wasting medpack.
l4d didn't tell you what you were doing wrong, it just killed you end game for an error in the starting moves, and I think it's that the cause of people not learning how to play it effectively. payday is more direct in that regard.
http://www.youtube.com/watch?v=xBZ86LwT8y0&feature=relmfu