Old ****ed up Cannondale roadie, peice o **** Gitane as a beater, and I use my Nishiki for bike camping
I've never used them myself, but I've heard that they strip more easily when you're truing.
I talked to a guy who had all different colors of alloy nipples on his wheel once, his wheel was pretty old and he had replaced spokes more than once. he said the nipples had never given him trouble.
I've never had them come loose or strip, but I have had them bond irrevocably w/ the spoke, despite using tenacious oil on the threads during the build process. I won't use them anymore except on fair weather bikes.
I live a mile from the ocean and ride along the coast daily. I will need to rebuild my aluminum-nippled wheels with brass before I can true them. What a PITA! Not worth the weight savings no matter where you live, IMO.
Aluminum nipples strip more easily (I've had a good many stuck aluminum nipples deform and round out using the correct park wrenches) and definitely should NOT be used twice in terms of wheel building. Not really worth it for me.