In reply to Robbie H:
A few thouhgts:
- for contouring and descending low volume is generally felt to be the way to go for trainers (theory is less volume = less movement = less twisting & rubbing)
- for rough terrain and particularly contouring then thin midsoles and low heels is generally considered the way to go (if you're not going for something with ankle support). The theory being the lower the foot/heel the less turning force on the ankle (think flat shoes vs. high heels).
- on wet grass Walsh tread is pretty much unbeatable.
- on wet rock Walsh tread isn't great (but suprisingly good on dry rock).
- on soft to firm snow Walsh tread works well.
For the above reasons Walsh (either Trainer or Racers)have a big following amongst the fell running, KIMM etc. regulars (and quite a few climbers use them as approach shoes). Only obvious downsides for this sort of use are lack of cushioning on roads and quick wear down of tread on roads.
A number of alternatives have been appearing over the last few years, notably New Balance and Addidas models with similar tread pattern to the Walsh and recently the Inov8 (which seem to be getting good reports). Build quality is important as this type of shoe takes a hammering, I don't have experince on the Walsh competitors, but whatever you get be prepared to glue them back together (especially toe rands).
If scrambling is more the use you need them for (rather than wet grass) then an approach shoe is probably the way to go, but pick one with a sensible toe. A lot of the approach shoes around seem to have toes that are next to useless for using on a edge/small ledge.
Also some of the resolers will resole other shoes with a Walsh type tread, which is worth considering if you have a pair of shoes that you feel are great, but the tread is just no good on wet grass.