Bought it, 4 hours play time. That is not much for me.
I've gotten a fair amount of gameplay out of L4D2, even though I perfer L4D1 gameplay wise and L4D2's weapons.
Jockey's are fucking stupid. I literally get pounced by any that spawn 95% of the time. They're just hunters that leap from closer distances but have alot more HP, making anything but shotguns or a HS with a sniper enough to drop it in time. Also, the shoving is delayed and they don't always jump when youde think they will.
Other then that, i'm fine with the special infected, just L4D1 feels like it plays alot better.
The Sniper isn't nerfed just so that they could have a better version, witches can't be power countered (Hard Rain, Shotgun), and yeah The onlything L4D2 has got going for it are the campaigns, the new type of mounted gun which you barely ever get to use (and are always set up in awkward angles) and the guns, ALL OF WHICH COULD HAVE BEEN DLC.
The Mutations are interesting but they are almost always competative or un-interesting enough to go play it again. Case and point: REALISTIC VERSUS WITH NO MEDKITS. VERSUS, NO REVIVING.
I'de say it's worth it if your getting it for like 10-15 dollars (I got my 3 copies for 30 or so), but if your going to buy it for your XboxLOL60 or some shit for 39.99, and you bought the original for like 59.99, i'de say no.