Well, I'd be hyped about this if they'd done it back when the expansion first came out. I was waiting for this, since I hadn't played the original yet past the first demo. But, they didn't... so now I've already got the original for a mere $20, and the same day I got it, they released that great 300MB patch giving me better graphics and more levels.
Considering opinions of the expansion are rather low, even by fans of the original (including myself), I'll happily stick with what I have.
As for the level designs having nothing to do with each other, I completely love that. I knew the whole game would not be that one town level from the start, the demo made that rather clear I thought. It completely breaks up the boredom to explore so many scenarios across so many map types. Anyone who's played a good amount of multiplayer FPS should be used to being dropped in a random map anyway.
The cutscenes weren't that bad at all. They weren't exactly groundbreaking, but honestly I don't know who'd expect that. I expected Serious Sam / Doom style carnage, and that's what I got. The story / cutscenes were certainly better than Serious Sam's annoying text-a-thon.
And the enemies... seriously, what's wrong with the enemies? So they're no Far Cry or Half Life 2, sure... but they fit their role perfectly. They're cannon fodder... easily comparible and in many ways better than the baddies of Sam and Halo 1/2. In Painkiller 2 I'd like to see some true tactics and such, sure, but again I think anyone expecting that here is simply playing the wrong game.