Don,
I have a set of the LimbSkins from ABS for my longbow.
They are like a tight spandex material that simply slips over the bow limb after unstringing it. They just stay put. I had mine on a 3 piece longbow, so they just kind of bunched up on the limb slightly.
I could not tell any difference in performance. They offer protection, as well as camouflage, if your limb woods are not naturally so.
I can not speak to adverse problems with the finish as I never had them soaking wet. They are very easy to remove and put back on, so if they did get wet, they could be removed and dried easily.