I'd like to hear from people who have used this clamp for an extended time in cold, wet, heat, dust and general muck.
That would be me, I guess!
I've used the RRS long lever clamp for about a year. I started out using it on the RRS ballhead, but soon switched it over to an Acratech GV2 (solely for weight reasons).
I shoot nature and find myself doing a fair bit of winter mountaineering. I've never had a hiccup with the lever head. I love how it will allow you to slide a plate back and forth when it is half open, but will prevent a plate with safety stops from completely coming out. Opening the lever all the way will allow you to drop or remove a camera or lens.
Works great for Canon, Sinar Hy6, Mamiya and Contax systems, different weights, lenses etc.
Two notes:
RRS cautions against some plates, as their dovetails aren't fully compatibile and could cause a "failure". We all know what that means. If your plates aren't RRS, check with them to be sure.
Be sure that the clamp is long enough to position, for example, a telephoto lens where you want it within the clamp. If you use safety stops, as I do, it means the range you can slide the plate in the clamp will be limited, so to avoid having to shoot with a slightly unbalanced rig, be sure your clamp is long enough.
Hope that helps,
-Brad