we did use center engine idle reverse all the time on the 727
on the 757 with the RR engines the idle is too high and the plane speeds up all the time (we fly a lot at low weight).
We are not allowed to taxi out on one engine (engine warming takes 5 min when cold) but we can do it when taxiing in ,i never notice any problems ,but its important to think what turns you have to make at low speed onto the stand to deside which engine you shut down.
Neil