'cos it has been mentioned here a few times: [MEDIA=youtube]dHrBpgoi9Ck[/MEDIA]
Dunno tbh, as I've not got one *but* if, like me, you're a fan of Zombie/Horror movies then you *must* buy Left-4-Dead. http://www.l4d.com/
Yes; you will get about 10 hours out of it in the SP mode. There are four different stories for you to complete, which are split into about four chapters each. Lots of typical Zombie scenarios - going through the sewers, abandoned hospital, subway, etc. Great fun and some really nice cinematics in it too.
Check online prices- it's $49.99 through Steam which is no longer favourable compared to shop prices with the shift in the USD-GBP rate. I managed to get mine through Amazon for £19.99, but they're now doing it for 26.99 with free delivery.