I think the primary appeal of the kickback coaster is the clean look. No cables, no levers of any sort on the bars, looks just like a SS to the casual observer, but you can get an overdrive high gear for the long flats and downhills. Personally, i think the best strategy is to think of what ratio you'd use for a singlespeed, and make it so the low gear is a bit under that, and the overdrve will be a bot higher. Best of both worlds.
The Bendix yellow and red band hubs have the high gear as the direct drive ratio, meaning that if you're running a 44/20, the high gear is the 44/20, and the low gear is lighter than that. The blue band, sachs, and new Sturmey's have the direct drive as the low gear, with an overdrive working with the planetary. I don't know what the ratios are with the bendix hubs, but the Sturmey and Sachs are 1:1 low, 1:1.38 high. (The Sachs torpedo is actually 1:1.37, but big deal, right?) These hubs are "better" b/c the low gear is the direct drive, so you're less prone to slipping when torquing up a hill in low gear.
Shifting while braking does occur, but so what? I think the typical complete-stop situation is likely to occur while you've been cruising in high gear. So, you stop and, in doing so, you automatically drop to your low gear, so you're ready to roll. If you have to come to a complete stop while in low gear, just give a double kick while braking, or give an extra kick just before you start rolling again. These hubs shift well while stationary, so no biggie. If you're rolling and just tap the brakes to scrub off a little speed, no big deal; you're already rolling, so just coast a second while kicking back into proper gear. Generally speaking, we're talking about 10degrees or so back to shift, and 15degrees or so back to brake. You can shift without braking, no problem.
This is all kinda moot, though, b/c SRAM has reintroduced the old Sachs automatic 2speeds. This year, they're calling it a SRAM Automatix, and they're offering it in 120mm OLD, with included spacers for running 130mm OLD. These'll shift at @11mph with 26" wheels. No need to kick back, except to brake.
Sorry to write a novel. I just like talking about these hubs, but no one outside of this forum seems to care about em.
-rob