I have two Dillon 550Bs. I don't track rounds per hour but would guess 400-500 would be fairly easy (possibly more). I don't reload for speed or for hours at a time.
Caliber conversion is easy. I have tool heads set up for each caliber I reload. I can switch calibers in less than five minutes without hurrying. If you need to switch from large to small primers, it takes a few minutes more. I have two 550bs simply so one can stay as a .45ACP press and the other .38 Spc, .38 Super, .40 S&W.
I bought both of mine used off Ebay and have had no problems. Dillon has the no BS lifetime warranty but I've not needed it.