Yeah, Stokemonkey is really nice. My wife and I were in Portland a few years ago and managed to get a test ride then. Todd and crew are really great and I think Stokemonkey is one of the better things since sliced bread. For our part though, it has a few key limitations. It needs a large enough frame to have sufficient clearance for the motor and it does take up cargo space on the xtra. We're trying to get through this as inexpensively as possible. Right now the frames we have are all too small for the Stokemonkey and we'd like to avoid the added cost of a new frame. Also, the Bionx we priced out at Nycewheels came in cheaper. A third consideration is distance. We're in Boston and NY adds up to fewer carbon miles for shipping than OR.
You mentioned other geared motors, but Stokemonkey and Bionx are the only two I know of that are commercially available to fit on an existing bike without some sort of custom kit. Are there others? I heard someone at MIT was working on one, but it didn't seem as advanced yet. I'm sure it'll be truly excellent when it hits prime time, but I don't know how long we can wait.