I understand that the Windbloc ACT 'membrane' is the same as that used in PowerShield. This membrane is actually a layer of PU glue, which, due to the way in which is is applied, forms a naturally 'perforated membrane' which cuts out most, but not all of the wind.
The only difference between Windbloc ACT and PowerShield seems to be the choice of face fabric; fleece in Windbloc, knitted or woven face in PowerShield.
For my views on soft shell, and some links to other OM threads, have a look at
this thread. Sadly, the link the the Rennies document at MEC seems to have died.
<my ice climbing chums have since pointed out to me that ice climbing sometimes
does involve lots of water cascading over you; after all, that's how many ice climbs are formed: by freezing of waterfalls. I consider this to be down to poor choice of route...>