Rim dynamo's are generally not the best option for long distance riding because of issues with reliability during inclement weather (ie rain). They tend to slip. Small imperfections in the rim's trueness will cause the dynamo to slip even when it's dry. Power output is lower than other dynamos. It doesn't even comply with StVZO's (German guidelines for vehicles on the road) 3W power output requirement at 15 km/h. I've also heard of wear issues with the small o-ring used to drive it. For cruising around town or short rides in dry weather it's probably ok. I wouldn't want to start a 1200k with one of those as my primary power source.