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.
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,