I have both a Berghaus Freeflow and a Deuter Futura which usw the trampoline style back. I didn't actively seek them out - it was just a feature that they happeneded to have. I think that they do work well and certainly seem to keep my back cooler than other rucksacks I've tried. That said, the normal cushioning type doesn't seem to be that bad anyway.
However, the downsides are that the pack is slightly less stable (further away from your back) and that they can be quite a bulky system, taking up space.
I've not been able to use it outside yet - I'm off to the Brecon Beacons in April, so I should be able to report back then.
First impressions are that it is quite long and roomy. It's the right length for me (I'm just over 6ft 1) but i'm quite skinny so it's not too tight either. It lofts up nicely and compresses down very small. It certainly feels very warm too, although that's from trying it inside the house.
Just a quick update - as Alpkit have said that it'll be a while before they are making sleeping bags again, I went for a Cumulus Mysterious Traveller 500, which has a rating of -7C, weighs about 1kg and cost £185. Bit more expensive than the old Pipedreams, but it's superb quality, made with Polish goose down (92:8 and 650+ fill power) and uses Pertex. Top-notch build quality too, it seems.
"And learn from experience of others. Early Himalayan expeditions never used expensive goretex, merino or paramo analogy clothing. Tests by respected technical fabric testing institutions have looked into Hillary's or was it Irvine's clothing. They determined their clothing was as effective as modern clothing on Everest. Easily capable of use up Everest."
It's for my undergraduate degree. I'll be in the north east in Teno nature park looking at how successful ecological restoration programmes have been ( http://www.tenerife.es/life/index.htm ). Prickly pear and agave invasives were removed and we want to see whether it's been successful in allowing juniper trees to regrow, which involves lots of counting of plants and trees. I'm really looking forward to it - there's loads of endemic plant species and interesting geology to study.
To echo Paddy - a good sun hat - it is your own patch of shade.
Definitely taking my sun hat! I picked up a big broad brimmed Craghoppers one last summer as I was working outside with English Heritage a lot and it was really useful.
Factor 50 - La Roche-Posay Anthelios is my choice; but expensive.
Thanks for the recommendation - I'll check it out.