It is ideal for a dyno you use occasionally which is the case for me. If you always use it you might be better off with a hub unit. This takes about 10-15 minutes to move from bike to bike depending on the mounts and how you have it set up. It spins at much higher RPMs than a hub unit which makes it easy to build as a small (and lighter) unit and it also gives it a mechanical efficiency advantage at higher RPMs. I mount mine on the rear and I have it there because it is audible, but to me not annoyingly so. It does not slip at all in wet weather and you would not want to use one if you ride in a lot of thick mud. You totally disengage it when not in use so no trouble at all when you want to pull off the wheel. I have the Trekking model powering an Edelux II. It is a great combination. It does get a bit dimmer when pedaling up a steep hill at 4 MPH, but I do not need as bright of a beam then either. It is very well made and not too bad to install, but you have to order the right type of mount (or mounts) for how you want to install it. I like the fact that I can mount it front or rear and use what ever hub and rims I already have, no need to rebuild a wheel and idle my Phil Wood hubs. I also like the fact that it is completely disengaged when not needed so no additional drag (unless you want to consider the very tiny bit of wind resistance for the unit attached to your frame).
Here is a post on another discussion on the Velogical. There are a lot of skeptics (that have not used it) and me, an actual owner of one.
http://www.bikeforums.net/electronic...mbination.html
Further down in the post you can see my power output curves. The unit I have puts out 2 watts at about 14 kph and 6 watts ah 23 kph. Not too shabby! They also make a higher output model for slower riders or ones that need to charge GPS or run multiple headlights, and a lower output model for faster riders that do not want to ground excess power back to the frame (which is what happens with most larger hub dynos).