I'd still probably wait. The 560 TI looks to be a great card.
Here's one thing you could do.... depending on the return policy of the store. I know Best Buy lifted their 15% restocking fee for a short period of time so a place like that would work.
I actually did this when my GTS 250 was being shipped to me.... go out and pick up a brand new card, charge it to credit, use it for a week or 2, return it.... $0 net cost, you basically just rented a card for a week.
That is if the 6800GT really is THAT bad.... I have one at home and it plays classic games just fine. I agree with an earlier post, load up some games like Doom3, HL2, UT2k4 and just enjoy the past. If FPSs aren't your style then KOTOR or another older rpg would be fun. Into RTSs? Pick up the original StarCraft or Warcraft 3.
There's a lot of older and fun stuff out there