I just bought a 650, I am still getting used to it....
I have owned a 550 since they came out.... if I am only doing short runs... 500 rds or less, I use the 550... that lack of a case feeder and the auto index slows the process down some, but caliber changes are a snap...
I too keep multiple tool heads and powder dispensers set up and ready to fly... for BOTH presses....
I try and plan my long runs out to where I am changing primer set ups as little as possible... lg vs sm.. I also stage some caliber runs to where a shell plate change is not needed, like .380 and .223 use the same shell plate...
Once your dies are set, swapping the shell plate is a 4 or 5 minute job, the cartridge drop tube bushings a couple of minutes. the most time spent is in adjusting powder charge...
Like all machines, it takes some getting used to, and it takes an investment in additional tool heads and powder measures... all are optional, but it saves a bunch of time and aggravation..