Zombie thread but since things have changed a bit over the last 5 years and I have tried both of the current hubs in both Freewheeling and Coaster forms I figured I would write a review of them

Sturmey Archer S2 or S2C,

I rode a freewheeling S2 for nearly 2 years and I have to say it works quite well. Especially if you are a control freak it's really easy to know what gear you are in while rolling the high gear is much louder when you aren't pedaling. It takes a while to learn to how much of a kickback is enough but spend a few hours on it and you should be fine. I wanted to switch to a Coaster so I tried a friends and was not happy with it at all every, time you brake you change gears, not a probelm if you are in high but if you aren't you have to remember to shift again before you start up. If you plan on Freewheeling the SA S-2 is a viable choice if you want a Coaster I would look at the SRAM. The Sturmey Acher's are available in 32h and 36h and lots of pretty colors ( Black, Silver, Red, Gold, Purple, and Turquoise)

SRAM Automatix

I actually tried a free wheel version before I bought my Sturmey Archer S2, I liked it I just liked the S2 more, the downside of this hub is you have no control over when it shifts, it changes gears at a set speed but the advantage is the shifts are much cleaner and acceleration is a lot better. The Coaster version of the SRAM hub really shines, you don't have to worry about downshifting when you hit the brakes, if you slow down below 10mph then it downshifts otherwise it stays in the high gear. climbing its a lot easier to downshift you let off just a bit and it drops down and then you can pedal again. Much more precise than the Sturmey Archer, I have about 25 miles of riding time on the SRAM now though it took me a lot less time to adjust to it than I expected. The SRAM hub is only available as a 36h but in addition to Coaster freewheel chain and belt drive as well as disk brake versions are available.

Weight wise the Sram coaster is about a half pound lighter than the Sturmey Archer coaster, I think the Sram freewheel version is 1/4lbs lighter than the Sturmey Archer though neither of the hubs is what I would call featherweight. Both use the standard 3 speed cog that is held in place with a retaining ring. The Sturmey Archer can take cogs from 13T through 22T the SRAM is limited to 15T to 22T If you change cogs replace the ring it's a safety issue and given the cost not a big deal at all. In theory they are both unsealed hubs and I have cleaned my S2 but it really didn't need it, the SRAM is even tighter looking as long as you don't submerge them, are you are riding a lot at the beach or on nasty winter roads you should be OK.