I've seen tons of them. Well OK, not tons, but I've seen at least ten or twelve. They show up on Ebay now and then.
I've read on several forums that they don't sound very good at all. most reports have come from Gibson enthusiasts.
Worst sounding Gibson bass, by those who played them. The Epi actually sounds better from I have heard from players that tried both. Hamer and USA Washburn actually made some very cool V basses.
If I ever buy a flying V, it will be an Edwards, made by ESP. http://www.espguitars.co.jp/edwards/fvb/E-FV-103B.html
I was just about to recommend the Edwards The Gibson V and Explorer basses from the 80's by and large suck. The 80's were a period when Gibson company was bought and sold several times and the quality of the instruments shows it.
Although I can not comment on flying V's, I've heard completely the opposite for Gibson explorer basses.
They're definitely not a good sounding bass, but they are rare and pretty valuable. I bought one of these cheapos on ebay for $150 with every intention of doing some serious mods. The bass out of the box is pretty mediocre (thoguh still better sounding than a Gibson), but I had every intention of doing an upgrade in PUPs, tuners, etc. and you really wouldn't want to butcher a real Gibson V just to get it sounding better.
is this a gibson? http://vids.myspace.com/index.cfm?fuseaction=vids.individual&VideoID=4024774 Jeff Pinkus!!
i have an epiphone flying V i got for £100, its pretty good, tone is still crap, but alot better then the gibson from what i heard, and also its light as a feather and the neck is great! for the price, i aint complaining!