I like it as an option. Less hard work on some rides (if you're used to it), and seems to be good for recovering legs that are sore from running. Even enjoyed last night's spin despite having removed my beard now!
If I had only one bike it would probably have gears though.
If you're experimenting with different gears trying to get "the right one", I don't think singlespeeding is for you. It takes a while to get used to working around having the wrong gear all the time by hamster wheeling/grinding at 1RPM more effectively.