I played it a bit on the long weekend, up to chapter 12 or so. I dont own any previous GoW titles, but did play through a mates GoW 3 last year.
I recon its not too bad, from a non-fanboy viewpoint. Its a button masher, with some frustrating sequences and puzzles but very entertaining, and some cool death blow animations.
Haven't sussed the MP yet but it appears to be offering PvP modes (team versus, CTF, etc), some Co-op, and even a solo mode. I did setup a MP character, and looks to have some depth to the MP character leveling and lots of class options with 4 primary characters, so not just a tack on.
Happy to join up with some GGers in the MP for some mashing action.