In reply to joedowell:
Just to chip in with some obvious advice but for me its been a case of what works/fits your feet - and you can't always tell in the shop.
I had a pair on Inov8 x-talon's and loved them. Lots of talk about the studs wearing down quick but seem ok if you stick to what they're meant for. Anyway, got that pair cheapish (£60) and couldn't face paying £90 but went Walshes instead. They're good, and I can see why people like them but they just don't hold my ankle as well (especially noticable when descending).
Got another pair of x-talons now; first time I've ever bought a second pair of any sort of footwear and have fallen in love all over again. Won a trail race (a soft one, to be fair...) in them straight out the box (literally).