I think it's a very well balanced game...and the ability to pick different upgrades for yourself is very cool. Weapon customization is good, and it's very fun, because it's not just "twitch-headshot" kills.
I don't know if I'd say it beats out Halo's multiplayer, but they're different games...hard to compare.
Anyway, I'd buy both if I had a 360...and you should too.
LEFT4DEAD411.COM
Bet with disolitude: Left4Dead will have a higher Metacritic rating than Project Origin, 3 months after the second game's release. (hasn't been 3 months but it looks like I won :-p )