First I want to appologize for my faulty keying (even more faulty than usual, you might say) while activating OE/OO-300 today.
Since summer 2008 I have used a CMOS sensor keyer for all my activations. This is lightweigt, small, has no moving parts, no adjustments that can go wrong and was cheap to assemble. Using it in sub-zero temperature with heavy wind reveals its down side: It works only when touched with the bare fingertips, you cannot use gloves! Big problem today! Temperature was around 0°C and the wind so strong, that my footsteps in the snow from ascending were totally covered/blown away when going down about 2 hours later.
I have now prepared a CW-operator glove. This is an old glove with the fingertips of thump and index cut away! I hope to try it one of the next weekends, actually I hope even more that the WX improves and I will not need it for a long, long time…
The minimum activation temperature for me so far about -10 or -12 C with relatively dry air. No problem with Palm Paddle, ATS3B, T1 ATU or FT817ND with internal batteries. The weather last weekend in Lapland was also quite warm, so could not test lower temperatures. I use thin gloves for mountain activity that you can find from sport shops.
I have, in the past, used a touch sensitive key. In mist, fog and rain (normal weather on hills here) it was useless and was soon abandoned. The Palm Paddle is the best that I have used - not perfect but close.
I never had any trouble with rain or wet weather with my keyer. I rember one activation were I was keying in a drizzle for some time. I did hide the FT-817 inside the backpack. Everything was soaking wet at the end, but the keyer was fine.
I do have a Palm Paddle and will take it to the summits soon. I prefer the touch keyer though, because it contains a memory keyer in a light weight enclosure.