You guys must be the lucky ones. I have what I believe to be the first Dillon 550 that rolled off their line and have not been so fortunate. Mine has flipped so many primers and reverse seated them that I finally dismantled the primer feed and now hand feed using a handheld Lee Auto Prime, regardless of caliber. It seems to be the only way to get a positive primer seating, for me.
I also use the powder dispenser in a separate step and hand manipulate it to drop the charges. Just once I loaded some personal defense rounds for my 38 snubbie using the full turret set-up and went to the range to test them only to find that more than 50% of the reloads did not get powder charges. Not very promising for defensive loads.
So, I take it for what it is and still use it. Mine is 26 years old this month, I got it for my 40th b-day. I still use it, but as a 2 stage turret: re-sizing, depriming and belling in one stage, but them priming and charging by hand, with seating and crimping in the second stage. I like the press and the thought that went into it and the folks at Dillon are very helpful if I need another shellplate or some new dies but otherwise, my 550 has a limited application for me. I will gladly admit though that the powder measure is the most consistent dispenser I own.
I am just very leery of not being able to visually verify that all the primers are properly seated and all powder charges properly dispensed before the bullets are seated and the 'reloaded' rounds are dropped into the collection bin. I am well aware of my foibles and this is one of them but at least I know that what I reload will shoot, unless the primer is a dud and that happens less frequently with my reloads than with factory ammo.