I read the comparison between the Dillon 650, Hornady and Lee progressive loaders. Very informative!

Once you set the dies in the Dillon block, they stay set. No matter how careful you are, lock nuts slip, and if you remove and replace dies, you have to check their setting each time. The block itself is not expensive ($15), and can be stored on a shelf if you remove the powder hopper (two cap screws). If you leave the hopper in place, the die block fits on a stand ($25), together with the shell plate and retaining pins.

The hardest station to set up on the Dillon is the powder funnel, which serves to expand and bell the case. The powder funnel comes with the caliber change kit. I purchase an extra powder die ($10), and leave it, adjusted, on the tool block. You can remove or attach the powder measure without affecting the die setting.

Dillon dies are expensive, nearly twice as much as a comparable RCBS set. However, they are optimized for use on a progressive press - tapered lead in the resizer, separate seating and crimping dies. The post in the resizing die can be used to force out a stuck case (which usually results in a broken rim). The seating die can be easily disassembled for cleaning, without changing the setting or removing the die from the block. You can also remove the decapping post completely, and drive a case out with a pin punch and hammer

The powder adjustment is just an hex head screw, with no calibrations. Someone makes a micrometer head to replace the screw. If you count turns and uses a divided difference approach (q.v., binary search), you can set up in 10 drops or less. For calibers I load a lot, I buy the complete setup for that caliber, which cuts changeover time (not including primers) to about 5 minutes.

Dillon has a special powder die for use with a rotary measure, like the RCBS, Hornady or Lyman. You have to operate it by hand, but it might be worth while with some problematic powders. I have a micrometer head on my RCBS measure, which makes it easy to set up and adjust.