I always check in at Gold * counters, and ALWAYS insist politely they tag bags with whatever their own "Priority" tagging is called, whether it be Varig, Luft, SQ, Ansett, Thai etc.
Always has been acceeded to cheerfully. Just did some Br.Midland flights, and all bagfs got the green BD Priority labels on them, and they came off first. BD were not even full * members at the time!
My personal experience is that United 1st or Priority tagged bags get excellent treatment.