That's a pretty good asessment of the MP bobbin, Ramcatt. One thing not mentioned is the ability to use different size thread spools, and have perfect tension of your choosing.
This bobbin will allow you to use even the tiny Pearsalls spools, and all you have to do is slide the thread tension spring to adjust it for your desired tension. Once adjusted, it doesn't move unless you want to change the setting.
At fifty bucks, yeah, it's pricey. But you really only need one to cover just about any tying situation. I've got dozens of other bobbins that sit empty since I started using my MP bobbin. The only thing I use my previous favorite Tiemco bobbin for is for the Danville Spiderweb I use to tie off parachute patterns on the post.
Great tool - I'd buy another in a heartbeat if I lost mine.