I tried optiboot a while back and it caused problems back then. One issue I brought up on the google code site was never resolved. I abandoned it then, it still has problems it seems and I abandoned it again. The amount of flash available was an improvement but if the sketches don't run as expected.....
It worked OK 'dry' it went flakey when I plugged in its shield with all the connections to my sensors and LCD panel. Putting the Duemilanove bootloader back cured it. I suspect the Uno would do the same as I can't see the different USB making any odds. I don't need another Arduino so I'm not currently in the market for a new one to chase it up and little desire to kick up a fuss. Its a pretty complex sketch and trying to pick the bones out to suit a new bootloader doesn't appeal. 