Tempest just isn't Tempest without a rotary controller, the same way Breakout isn't Breakout without a paddle controller (which explains why Breakout 2000 still irritates me! ) It's all about the controller. What's a driving game without a steering wheel? Marble Madness without a trackball? Star Wars without a flight controller? etc. etc.
When I made my rotary controllers, some people loved them and some people thought they were too sensitive. If you like the sensitivity though, the control is infinitely better than using the pad. It's definitely better if you have a chance to try something before you buy it. Especially if you are spending $75+ on it. In my experience, if you don't find a controller easy to use within half an hour or so of playtime you probably never will.
Btw, I hope everyone is still enjoying their rotary controllers. Hopefully those optical encoders are still going strong.
Jeff