Finaly i bought it today!! GREAT GAME!! I am on level 2 now!!

Btw, how scripted is the game? At some points in the demo I could swear some of the enemies respawned again and again if I didn't rush, which made the game feel a little annoying.

Numbers of enemies is always limited. Sometimes there is a lot of them and if you're camping in one place it can appear as endless spawn, however if you rush at them some scripts and general situation can change.

That's how it is - until they run out.

As for the original question: I did not play Painkiller, so I can't compare. But, I definiately like the story.