Albin; you lucky duck!
I started reloading in the mid '50's, and the only progressive reloader for pistols was the Star; a very expensive tool.
I put up with a single stage press for over 30 years. About 10 years or so ago, I bought a Dillon Square Deal B; I absolutely love it, and actually prefer it to the 550, as the machine is smaller, and I can get closer to it. I have reloaded thousands of .45 ACP, .44 mag, .357, and 9mm's with it.
I bought a 550 so I could accomodate rifle cartridges, and also use standard 7/8 x 14 dies. I like it a lot, and it really cranks .223's out at a fabulous rate. It is particularly nice in that if you buy an inexpensive extra tool head, your dies are already set up and adjusted. Just slide the old tool head out, the new one in, change the shell holder, and rock and roll.
Dillon has fantastic service; they will repair any of their presses, no matter what happened to it. Run over it with your truck? No problem, just send it in. Bought it used, no problem, just send it in. Something doesn't work right, just call, and if they can't fix it over the phone, they will send you a replacement. When they say that we don't want our customers suffering in silence, they really mean it.
Check the machines used by all the professional pistol competitors; virtually all are Dillon.
For someone who has seen many improvements come and go, the Dillon line is something that will definitely stay; it is absolutely terrific. Walt