I'm not a big fan of them. Probably because I started tying without one and now they just seem to get in the way. I don't usually rotary tie, but I do for winding some body materials -- eg, a coarse dubbed thread loop for a scud. In this case, I throw a half hitch and rest my bobbin on the tying surface off to my right while I wind the body.

As a general rule, I prefer to minimize the number of tools on my bench. For me, more tools means more clutter and less efficiency.