In reply to goldmember:
I did it for the first time last year. It's hilly-ish. One long steady one at about half way and then a shorter one near the end which to be honest isn't really an issue cos you're reaching for home. Couple of sections are a bit rough and muddy.
People rave about it but I found the sections of running on the side of the road a bit annoying. Good atmosphere though.
I'll be doing it again though as build up for a half in March (Cardiff world champs)
There is a half marathon starting in edgeley Park in early september if you're interested.