INOV8 Mudclaw 300s have been the best fell shoes I've ever had (the ones pictured above in DrPatrickBarry's post). They were comfortable from the first 6 mile outing and I didn't have any issues when I next wore them on the 42mile High Peak Marathon! They are so grippy and I've worn them on all sorts of felly terrain (boggy, rocky, grassy etc). If I could wear them on all my runs I would but for hard trail and long distance (anything over 25miles) I use Roclite 315s because they have more cushion and are kinder to my feet on hard surfaces. I'm on my third pair but have had an issue with my most recent pair (new colours but old style). They seem to be a slightly different fit and they gave me blisters on the first day of my 140 mile Cornish Coast Path run which was a bit annoying to say the least. I have just resurrected an old pair to run the Lakeland 50 in (didn't want to risk it in new shoes). It was like putting on comfy slippers My feet felt fine all the way through and I haven't had any problems since the race. I'm now going to try on different roclites in 6.5s and 7s until I find a pair that fit perfectly and that I can trust as they aren't making the old style one now.
Having said that, you have to find what works for you because we're all different!