I'll start by saying I've never even seen one. Maybe I'm set in my ways.
1. I find that most coyotes come in from the direction the call is facing, that might be because I face the call in the direction I expect the coyote to come from.
2. I like to get elevation to my call and like to set it in a bush to get it off the ground, pretty hard to get it to rotate in a bush.
3. I have had little luck with a decoy on the ground in cover because coyotes don't see the movement until it surprises them, I would think the same would happen with them coming upon a revolving caller.
4. Movement can be the demise of a stand, can something as large as a caller spinning be comforting or enticing to coyote. I use decoys but they are small and non-threatening.
5. One more thing to suck power out of your batteries or to fail to work. It is hard enough to keep callers working in the dust, damp and cold of the predator hunting environment.
6. Where I hunt it isn't always easy to find a level spot to set up on. I can remember when movement decoys first came out having to pack a piece of plywood to set up on so they wouldn't tip over.
Just some random thoughts on a revolving caller.