I use one all the time and really like it. The adjustment (shifting) is easier if you are not up mashing the pedals, but it's never difficult. Shimano can take their units and stuff 'em. After a small retaining pin broke in mine, they told me my only possible solution would be to buy a new unit, they stopped making parts when they changed the unit. So I bought a new one, a Nuvinci and have been very happy with it in daily use for the past two years.

Marc