I built a wheel with one for a Fairdale Coaster a few years ago. The difference between the two gears is huge, so you're either in a super-spinny "climbing" gear or a big ol' "cruising" gear, and there's nothing in between. Every time you hit the brake you shift the gear, so you have to remember to double-tap the brake in order to stay in the same gear when you slow down. Starting up from a dead stop, you'll often find that you're in the big gear, requiring you to tap the brake just as you're trying to accelerate.
Honestly, I thought it was a huge PITA. I sold the bike on Craigslist and lied to the guy who bought it about how great it was. I may burn in hell for that, but it was worth it to be rid of the thing.