Great game with a little extra punch.
If you've already played the single player campaign you're not missing that much. Really get the game if you plan on using the editor and wanna experience the game on PC online. Do not get it if you already own an Xbox 360 just wait for Gears of War 2.
Wish I could give the game a 9.5 but it has that feeling of "been there done that." Hopefully once I start tinkering with the editor I can feel more satisfied. A great game though and co-op online is free as well as all the other game modes. Only things you pay for is so you can invite people, host player and ranked matches, and multiplayer achievements. Single player achievements are free.
Also there have been numerous issues for people to get the game to run. Seems Epic did not test the game well enough before releasing it.