A few of us at the TSG have been testing these suits over the last few months:
http://www.corstonsinclair.com/prodView.asp?idproduct=951
We all ended up with the hi-vis Saturn Yellow versions, which caused some hilarity initially, but in retrospect, it's hard to lose someone in a glowing suit! They're incredibly soft and supple, and very warm too - I've waded up the Speedwell streamway many times in one now and it's held up well. Not really intended as an 'immersion' suit, but nevertheless they keep most of the water out due to the large 'flap' seals on the zips. A velcroed hip pocket slot is the only other potential ingress point, but it's not too bad really.
The
weak spot from a caving perspective is the zip, as it's a normal 'clothing' zip, and not chunky enough to deal with mud and grit, so they need to be kept clean, otherwise it would get wrecked. The
strong point from a caving perspective is that the elasticated fabric backing to the plastic prevents a tear 'running'. They
will tear on rough stuff, but it self-seals to a certain degree, and can then easily be repaired with AquaSure or similar at home.
One other point (which I'm guessing applies to most suits to some degree) is the fit - they only do small, medium, large and x-large. A large fits me well, albeit with slightly too-short sleeves. However, others struggle to lift their arms up fully as the torso isn't long enough. Aunty Ann's fits so perfectly she wears it all the time. Richard T has used one exclusively for over two years, and it's still going strong. So I guess it's the usual compromise in that respect, but overall I'm quite happy with mine, and it was a lot cheaper than a Meander.
One other unexpected bonus was that being hi-vis, it was legally OK to wear onsite for rope-access work, and being on a roof in Manchester for most of last summer meant it got some usage! Very toasty in wind and rain. Got more damage there than underground though, as there was so much sharp metal everywhere.