For Sale: Shimano Ultegra SL 6600 STI Double 10 Speed new and unused

^ Do you have any sources for those issues?
Genuinely interested as I don't think I've ever heard of faults like those on these shifters?

Re 6600 being better than 6700:

There's simply no way around it: the new hidden cables look better but the more convoluted routing also yields noticeably more friction than before – and unfortunately, Shimano's 1:2 cable pull ratio makes it more sensitive to that friction than its main competition. Whereas the Ultegra 6600 levers feel silky smooth, light and positively connected to the derailleurs, 6700's feel is more vague and heavier and the connection is slightly muddied.

http://www.cyclingnews.com/reviews/shimano-ultegra-6700-group