There's a couple of sites in my Yellow Pages that have good vampire FAQs...the UESP and GameFAQs, I think. Basically, the way I see the whole vampire thing is this; unless you want to become a vampire full-time and slaughter everybody, there are three reasons for getting bitten:
http://isengard.imperiex.net/~neoxro...eltonbrand.jpg http://isengard.imperiex.net/~neoxro...lightofday.jpg
and
http://isengard.imperiex.net/~neoxro...ue/darksun.jpg
The first is something you can only get by having Goldbrand and by doing certain things as a vampire. The last two can only be gotten through doing one of the Aundae quests, which is one of the vampire clans. All the other vamp rewards will disappear when you're cured, so there doesn't seem to be much point in doing them, except as a means to the above ends. I'm definitely going vamp when my current character is ready for it (i.e. can walk into the Aundae stronghold and not die while the bastards bite him, waiting to contract Polyphoric Hemophilia with 75% Disease Resistance...) just for those three lovely items to add to my collection.