The Sram Automatix is an automatic shifting 2 speed hub. It uses centrifugal force to shift. Mine consistently shifts at 11.5mph. Works great for me for riding in traffic, as I can sprint from a stop and it shifts for me at just the right time. I end up at my 17-18mph cruising speed quite quickly. If I need to climb a hill in low, I simply keep my speed at about 10 mph and spin up the hill in low.

My new setup has a slightly lower top gear, at 66 gear inches, than my old 3 speed setup did, at 74 gear inches. The new setup puts the gears in better ranges for my easy, high cadence spinning preferences, so my average speeds are faster now than they were with the old setup. I used to find that gear 2 was too easy and gear 3 was too hard to spin with.