Another question is will they work on the next Canon DSLR?
Twice now, when Canon updated lenses on their DSLR's, Sigma lenses stopped working because of errors in the way they reverse engineer Canon's lens system. Those that had current production lenses could send them in for a upgrade. It cost me over $100 to upgrade my 105mm macro, but my other 4 lenses could not be upgraded and became paperweights They just gave error 99.
Since then, I've been very reluctant to invest big $$ in Sigma lenses. Its not a savings if they will not work on future cameras.
Hopefully such a circumstance would be overcome with the USB hub. It should be able to update firmware as well as fine tune focusing...