In reply to Choss:
Not this year - but it was my first marathon a few years back and I raised over £1,500 for Medecins sans Frontieres which I was quite pleased about.
Its a great day out for runners and spectators and for 75% of runners its a fun run - which is why when you watch the 4 hour+ runners they're in a world of pain because its all about completing the distance. The faster guys are in pain since as Nick says, they're racing and it hurts.
In my opinion, trying to run a marathon in under 3 hours (my current goal) is harder than running an ultra for 18 hours (its just over with more quickly). But whatever the level its a great achievement and everyone crossing the line deserves congratulations no matter how hard they worked.
Anyway, what stuck with me was the noise and enthusiasm from the crowd for the whole race - on a sunny day the turnout is huge and it makes a massive difference to runners. Despite getting cramps at mile 22 (and a nice lady in the crowd trying to offer me water and Ibuprofen, and lots of encouragement) I really enjoyed it.
Good luck to anyone doing it, especially if you're trying the distance for the first time.
Post edited at 11:33