I got a Dillon SDB last year after some good advice from a couple of members here and have been delighted with it (was considering their 550 also but since I only am reloading handgun cartridges--and that's all I had planned to do--went with the SDB due to its auto indexing and somewhat easier (for me) die system). I reload 38 special, 44 special, and 45 colt cartridges. ........................
Actually the 550 is faster than it looks. I'm used to my old RCBS progressive and would have to insert a case in station 1, put a bullet on the case in station 5, and pull the handle.
With the 550, it's the same deal, except that my thumb hits the star wheel on the way to station 3 to place a bullet. It's pretty automatic to do so advancing the shell plate is easy and takes very little time.
One thing I really appreciate it that if I suspect something did not go right, I can pull the case from wherever it is and check - then put it back in the shell plate. Same thong for set up
2 things I really like - and this probably goes for all the Dillon equipment - is the primer feed and seating is very positive and consistent. And the powder measure is also very consistent.
Only things I don't like - it's 4 stations instead of 5 so I can't use my powder checker dies as easily, and if I forget to advance the shell plate, I get a powder dump at station 2. But not mislead anyone, if there is no case under the powder measure, the powder measure does not activate. What I'm talking about is getting momentarily distracted and neglecting to rotate the shell plate. But that's purely my fault - lesson learned for not paying attention.
Must....Pay....Attention.