I bought a Sturmey Archer S3X right after they were first released. For those that aren't aware, the S3X is a three speed fixed gear hub. It was the first hub of this type to be manufactured for about forty years, or more. I had been riding fixed on and off for a couple of years, but I never enjoyed it when I wasn't riding on relatively flat routes or for distances of greater than a couple of miles. The S3X solved a lot of the problems that I had with riding fixed in mixed terrain due to the fact that it allows you to change gear ratios on fly. Now I wasn't spinning out on down-hills or grinding exhaustively on climbs. My knees felt much better.
I purchased the hub as a part of an Alex SUB wheel set (which was the only way that it was available for purchase in the first couple of months after it's North American release). I installed it on my 2007 Raleigh One Way, but I didn't use the front wheel that came with, because I had recently built a wheel that paired a Sun CR20 rim with a Sturmey Archer XFDD front hub (which contains a drum brake and a 2.4W dynamo, which I used to power an Inoled Extreme headlight and LED taillight).
I built this bike with the intention of creating the ultimate, all-weather-condition commuter bike.
Once I had installed the hub I had a hard time setting up the shifting. I had to mount a bracket on the chain stay that would hold the shifter cable in place. No matter what I did, how hard I tightened it or what kind of shims I put under it, the bracket had a tendency to slip, which would totally throw off the shifting. Once I finally got the bracket mounted correctly, I had trouble adjusting the shifting chain that connects the cable to the hub, despite following the included instructions for hub mounting and adjusting slavishly. When I was finally satisfied that I had adjusted the shift cable and chain as well as I possibly could, I found that the indexed stops on the shifter weren't positioned exactly where they should be in order to shift the gears correctly. I would have to use the shifter more as a friction shifter, adjusting the play until I could feel the gears change. This was slightly less than ideal, but the hub seemed to work as well as I had expected it to, despite these problems, once I had it set up. I started riding the bike several times a week for my 30 mile round trip commute to work.
Within a few weeks I started to experience problems. I found that I would have a tendency when shifting to land in a dead spot between the bottom and middle gears, where the cog would spin freely, disengaged from either gear. Then I noticed that the bottom gear would sometimes slip when I attempted to apply back pressure to slow down. This problem quickly progressed until the bottom gear operated more like a free wheel. Soon the middle gear was failing like this as well. The top gear (direct drive) continued to function like a normal fixed gear hub, but I couldn't ride in either of the other gears. I stopped riding the bike altogether.
Then I accidentally let the bike fall to the ground (not a big fall, mind you, just a normal topple from vertical position onto its side) when I was moving it around in my garage. This caused the surprisingly brittle outer casing of the bar-end shift lever to break. Now both the hub and the shifter were broken, and I was ready to totally write off the S3X hub as a moderately expensive failed experiment.
The bike sat untouched in my garage for over two years until I sent an email to address on the Sturmey Archer USA website last week. I got a response back in just a few hours. In the response email a representative asked for my mailing address. A couple hours later I got another email with tracking numbers for a package shipped via ups. Less than a week later a box arrived on my doorstep that contained what appeared to be a complete replacement of all of the internal gear assembly of the S3X hub. Alas, I don't have a tool set sufficient for disassembly of the hub, so I took my bike to a shop today and asked them to work on the hub and to order a replacement shift-lever.
I am eagerly awaiting the chance to ride my ultimate commuter project bike again. It should be back from the shop next week. But I'm going out of town, so it might be a long time before I get to go for a spin.