I see lots of tribute and cover bands (including Fleetwood Mac) and I haven't been disappointed yet. I'm thinking the best ones (out of possibly several?) must stand out enough to get bookings and develop a following.
I missed a recent Queen tribute as I was already committed for the evening.
I'm turning down an upcoming Dennis DeYoung show because, although I like the venue (casino auditorium we regularly attend), they're bringing in seats (not surprising). I'm done with live music seating, it's standing-only for me. What's the point of hearing "Babe" (Cornerstone) live if I can't slow dance to it? Seats would also suck for Hard Rock tributes like Ozzy/Sabbath and Led Zeppelin. Staying seated for last year's Journey/Def Leppard show sucked as well as I'm used to dancing to Molly Ringwald's cover of "Faithfully" (we all know chicks love it when you dance with them, even if just the slow stuff...and I don't drink enough anymore for the other types).
So that's what I enjoy most about tribute/cover bands, the standing-only and the price that usually goes with it ($10.00 - $15.00 range).
I make an exception for Brit Floyd.