Have a 2007 Litespeed 10 spd with compact crankset (Shimano R700). The crankarm fixing bolt failed recently with unfortunate results to my backside. Am considering going with Ultegra 6750 compact crankset with Dura-Ace bottom bracket. Does anyone know if this is a compatible upgrade?
Yes, all the 10-speed Shimano 34/50 Hollowtech 2 cranks are more or less drop-in replacements for one another. ("More or less" only because they could be subject to very small differences in where the rings fall, so adjusting the FD may be necessary.) You don't need to change BBs if the old one isn't worn out.