I have a Sinclair concentricity gauge. I use it on occasion, as needed. It isn't something I use all the time. It can be very revealing of bad dies, or bad practices for sure. And when you need it, you really need it.
Magnetospeed is great too. No way would I go back to a chrono with skyscreens. Life is too short for that crap. Painstaking setup. Finicky light. Missed shots. I went through several different models with skyscreens. Never again.
