I wasn't expecting to like it, but this is a great show. It's funny and the plot is actually thought through and (sort of) consistent. It's not just serving the jokes. Especially the second season has a serious touch.
That aside, I gotta say it's all thanks to 'the Devil' that I kept watching. Ray Wise plays him brilliantly: he is sadistic, intimidating, funny and still has room left for rare moments of affection(?). Much of the cast looks boring compared to him: I never really liked any of the 'good' characters, but that makes it funnier when they're the victim of whatever the episode is about.
Altogether, 'Reaper' is definitely worth a watch. It's too bad it got canceled.