Bungie.net is a great place to gather data from the game.... In the lower left corner there is a "recently completed campaigns" tool. I'm seeing pretty much every one that played it on NORMAL go well over 20 hours... I'm sure there are a few people who finish it in a "marathon" that can do it in less, but it makes me wonder how many "reviewers" truly played the full game.

Regardless, Bungie.net is a cool site...

*edit* scratch that first part.  I don't think it is reporting full games, though that's what it is saying... I'll see if I can find something else on there... the bungie.net is cool part stands, though. 

I got a chance to get my hands on Halo 3 over the weekend, my brother came to visit. We played a bit of co-op, and then I played some single player by myself ... on Heroic.

Those bastard alien snipers were annihilating me left and right.

I'm guessing that those who are big into Halo can probably run through it in under 10 hours, but the average player will take longer, especially if they play on a harder difficulty.

It took me about 12 hours on Normal, though im hardly a fantastic Halo player

Same thing here starcraft, 12 hours was my maximum hours. I didn't find the hidden skulls yet. I think I'm going to play that co-op with one of my co-workers. I tried to play Heroic by myself, I was getting thrashed from every corner. Then I started over and put it on normal.

Excellent game. Multiplayer is awesome.

Lol, i havent even thought about looking for the skulls yet. Im not big on the multiplayer, but im still gonna get 25-35 hours out of this game between higher difficulties and skull-finding, not even including future co-op days with friends.

Yeah I am planning to do some co-op action once I get my copy. I haven't played much Halo, so I am going to need my best friend to "carry me" through our co-op missions.