Game is the shit. The randomly generated weaponry works pretty much like Diablo and is a very effective carrot on a stick...the combat is lots of fun...levelling up is fun just like in Diablo where you can't wait to level up and get that next skill point. The graphics and environment are sweet. What else do you want? I've just been playing co-op with a friend who has two completely legal copies and it's awesome.
The downsides...running out of ammo is really annoying; I guess Diablo had durability of items that you had to go back and repair, but first of all, they took a LONG time to degrade, and second, you had town portals so it was no big deal to go back and fix them. Here if you run out of ammo during a big fight, you get to eat a dick, walk back to town, and come back to find the boss at full health again.
The other downside is that the classes don't seem distinct from each other. I'm playing a Siren and my friend's a Hunter and aside from having different special abilities, which we don't use all that often, the two play pretty much the same. Haven't tried the other two but since everyone can use the same weapons equally well, it seems like there's little point in having different classes.