I'm wondering whether its just the constant humidity down here or just the amount of use they get in a short space of time. Some people have no dramas whatsoever, Flyfisher just blows his down mat up by mouth and I think he has had it a long time...
Whatever... the PO mats lasted 2 yrs, the exped (And their replacements..) lasted one, the neo has held up pretty well for 1 summer so far.
This in mind, I dont trust inflatable mattresses... When talking about warmth, to me that means a real possibility of snow camping and I just think there are better/safer ways than a single mat.
Last winter we used the neo (U/L) to -7/8 by simply carrying these:
http://cgi.ebay.com.au/ws/eBayISAPI.dll ... :MESELX:IT (

) (but any thin cc foam would do..)
They were cut up into 3rds and we used 2 of these 3rds (now about 1mx 70cm ea). We used one over, one under. I would just be making up a temperature rating (as do all the manufacturers) but (to me) they were as warm as the synmat (at least). Likely close to the 500g mark and they pack up easily (also give a nice warm seat or kneeling pad)..
Downmats I have nothing against, as i said i just dont think theyre necessarily the best way... Added to that you have down in a closed vessel with no effective ventilation, not ideal and not the same situation with a sleeping bag.
I also have seen issues with separation of the tubes, i dont think lengthways tubes are the best idea and they seem common.
This is all quite general (and repetitive) but some applies to the Kooka's. If your set on a single down mat they would be my choice.
All that said, the neo (which is being sold on) is being replaced by the neo-trekker model. A bit heavier, tougher, Cheaper (and to replace) and they will be used the same way as the neo. This might seem a step backwards but has been a lesson learn't at considerable expense.