I think the 50th Anniversary designation is not that big of a deal, apparently its the Fender Anniversary, not the Jazz bass, so it applies to anything from 96. Nothing special issue about the bass (am I right on this?).
I'm very tempted to pull the trigger even though I prefer P necks. I'm having a lot of fun with my Hot Rod P and wouldn't rule out a nice Jazz for a good price. MIJ's are usually excellent and this one looks to be in great shape. $799 BIN is pretty good, wish I had the funds to go for it...
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=120312626393