I got to about 95% done I think and it took me what must have been 55-60 hours I think. In the scheme of things 50+ hours of gameplay for £24 is a bit better than the 6 hours or so for Modern Warfare (at least if youre like me and dont like playing FPSs online much). Combined with a second replay probably taking 30 hours, compared to another 5 hours for such a game, and it is pretty good value for money
Mind you this was mostly on Easy mode, which is just a little short of being as WG said, an interactive story. The biggest shame is how there is so much difference between Easy and normal mode. Easy doesnt have any form of a challenge except in what are essentially the boss fights, whilst in Normal mode pretty much every conflict will end with a party-wipe if you arent careful (at least I found this) and I dont think id have much of a chance against the bosses bar a lot of frustration and spending more time in the paused combat screen than actually fighting or even reading the codex!
Will give it a month or so (probably a few weeks) before starting a play through as a badass mage. The only thing that I think will suck is I am guessing the mages wont have the cool slow-mo finishing moves for the larger enemies...
Step surfing on an ogre
More dragon riding
Only other gripe is that the achievements on the PC version dont tie in to the MS gamerscore thing