Seriously, 8-10 hours is being insanely generous. It's definitely under 8 hours and I was taking my sweet time with it. I really think it's barely over 6 hours if that.
A game doesn't need to be long to be amazing, I don't get why people think this is the case. If Bioshock was 12 hours instead of the 15-20 it is supposed to be it will still be great and it doesn't have multiplayer even.
I can tell you I was pissed at the length of the game, but on the other hand it does everything really well (both single player and multiplayer) and I've played it 3 times already cause it's that good.
The multiplayer is very good too, an intense battle cause there are only 4 members on each team. So much more team work than almost any shooter almost cause of the system and how the matches work.
Also, it is still the best looking game so far, until the big games hit later this year and it almost single handedly made 3rd person shooters right up there with first person in multiplayer which was unheard of before.
Just look at all the 3rd person shooters that are coming out now, just look at how it effected Metal Gear Solid for evidence as to how significant a game it is. Kojima is borrowing a lot from Gears and for good reason, from the gameplay we've seen in MGS 4 it looks like the combat is vastly improved specifically because it playes a lot more like gears now.
it's short but great, and if you play it in co-op it's even better.
Seriously, just go play with someone else the whole game or even a few levels and you see why it deserves the score.