I'm all for rotary vises. I have 2, a Griffin Odyssey and a Danvise (and a Griffin 2A for travel). As mentioned, not only can you position the hook to attach material with ease on any side (or apply head cement), and inspect the fly and apply dubbing or chenille or ribbing evenly, BUT you are also easier on your materials and temper. With a stationary vise and changing hands as you wrap, two bad things can happen. 1) You lose the grip on materials, 2) the flex and stress on the material as you change hands and tension causes the material (usually a feather) to break. With the in-line rotary, tension is even, the material is held basically stationary and stable. It is also faster, esp. on flies like WBs. The only thing to remember is to put on a half hitch and place the thread over the bobbin holder before rotating.