It's definitely repetitive, but fun in a mindless hack-and-slash way. I found the story and world pretty entertaining.
The mechanic where you gain health by executing enemies is sometimes problematic (you can wind up in no-win situations where the only way to get health is to expose yourself to enemies and end up dying, which is frustrating), but when it works it can lead to some exhilarating risk/reward situations. The base idea is good, but it probably could have used a little more balancing and tweaking to really shine.
Campaign took me three nights to beat. I haven't tried the multiplayer.
It's no Gears of War in terms of content and polish, and I'm glad I didn't pay $60 at release, but it was fun and I'm glad I played it.