In my opinion, it is. It's the funnest FPS I've played since Half-Life. There are technical issues, but those'll get worked out. The Halo community is a pretty cool one to boot, and they're gonna be all over those editing tools like mud on a pig. I'm expecting some very cool MP maps for this game, as well as some sweet mods.
How happy is the blameless Vestal's lot!
The world forgetting, by the world forgot
Eternal sunshine of the spotless mind!
Each pray'r accepted, and each wish resign'd.