I just replaced all of the 921 bulbs in our TT with these
http://www.ebay.com/itm/251487597974 48-LED panels. $20 for 10 of them, so only $2 per light!
My take on them:
The socket adapters are kind of cheap, and I had to straighten the wires to get them making contact, but once I did that, they work fine and the socket adapter is snug in the light. Brightness wise these are quite close to the light output of the factory 921 bulbs, though a bit more directional, not quite as wide spread, but that's to be expected with LEDs. These "warm" white ones color wise are somewhere between the typical blue tinted "white" LED's and the typical "yellow" incandescent bulb, quite a pleasing color.
I might make and post a youtube video comparison later on if I feel so inclined.