Hey Dan,
I was recently in the market for a good pair of wading boots also, to replace my old scierra wading boots which fell apart after a couple of years, and opted for some vision hopper boots. They are a tough, but very light and comfortable boot. I bought the vibram sole with studs from a shop online (north east tackle). They are quite expensive, but in my opinion worth it! My old ones were about 40 quid and rubbish, these are only just over twice the price.
From what i gather, boots in general can be a bit hit or miss...with some falling apart after half a season. I'm sure others can recommend some other good brands too.
As for sole type, different people prefer different soles for different rivers etc..but last i heard rubber was best to help prevent spread disease etc..especially if you are travelling as some places abroad you are not allowed to use felt. Happy hunting!
cheers
J