I have the imotion 3 on my swobo otis. It definitely is a noisy little thing as compared to a normal derailleur based system, but I find the sound of it actually quite soothing. It's pretty reliable, shifts well, and was incredibly easy to get properly tuned (one twist of the tensioner). Most of the reviews of the sturmy and shimano systems I've read all seemed to hold the SRAM models as the gold standard.