A short one in the dark, but a test nevertheless.
This thing should probably come with a health warning, because it will give you The Fear. On the other hand, it really is fun, in a way unlike any other bike transmission I've tried.
First things first - make sure it's adjusted properly before riding, and run the cable bare as much as possible. You do NOT want to find the neutral between "1" and "2", and an old-fashioned trigger might have been better than the nice, but potentially in-betweeny bar-end shifter.
I put it in middle gear (63") to start off with. It feels almost the same as a normal fixie, albeit one with a fairly slack chain. The bike doesn't feel any heavier than with the Goldtec track hub, which surprised me. Then the weirdness happens. You shift gear and your cadence changes, with the pedals suddenly speeding up. Eek. Now I was in a 53" gear, which is really, really low for fixed. This is slightly grindy but it will probably run in over the first couple of hundred miles. It's nice to climb hills on fixed without having to stand on the pedals, and headwinds suddenly cease to be an issue.
Then I got it onto a long downhill and put it in the top gear, which is 84" in this case. This is direct drive and is completely silent. I overtook another couple of cyclists in the dark, got to the roundabout and changed down to the 52" gear again. Going down from "3" to "1" in one sweep is extremely weird because of the sudden huge increase in cadence; now I know what a car engine feels like when it's being driven by my mother. On the other hand, I could effectively leg-brake on steep hills by going down through the gears, just as in a car. The lowest gear allows the bike to be held on gradients where I'd normally need the brake to avoid running away.
I half-climbed the steepest hill in the village and nothing slipped or broke. Then I came home again, giving it a bit of a whizz in top gear again when I picked up a headwind. The ratios are actually well-chosen, although too wide for time-trialling (I'll stick it in direct drive and leave it there, just using the other gears to warm up and get to the start without plugging along at 50rpm like normal).
I like it more than I thought I would. It would be nice if it had zero lash, but I suspect it's the minimum achievable considering what's going on inside the hub. It has no "purity" like a proper fixed gear; this is something you ride for fun, because you want gears but don't want to run a rear brake or because you have too many hills for one ratio. It is, however, not an easy or novice option, because this will bite you even harder than a normal fix if you don't treat it with respect.
