I'm happy with my SB-800's and don't plan on upgrading until they fall apart.
As far as paying extra for TTL...well, TTL is worth it, especially if you know how to use it. Shooting manual flash would be almost impossible in a lot of the conditions I shoot in. At a reception, where you are bouncing flash with constantly changing distances, I don't think I could be nearly as effective constantly trying to calculate manual changes to a flash as a couple is moving towards and away from me on the dance floor. It's silly to even contemplate.
For me, TTL that works seamlessly and accurately on my hot shoe is an essential function of a hot shoe mounted flash, and yes, I am willing to pay for that function. Just, IMO, the SB800's do a great job and they are a couple hundred bucks cheaper.