550B owner here - Love it - LOVE IT!!! Ok got that out of my system.
I have had several calls to Dillon not because the press was not functioning but just silly questions and they always are kind and responsive. They have sent out replacement parts when they were not even needed but to have as backup just in case
You can get some really good deals on used plates, tool heads, dies. That will keep your cost down as you add calibers to the mix. I can do a caliber conversion on the Dillon in about 5-10 minutes depending.
I like the manual index because it keeps me involved in the entire process.
I would gladly buy another and wish I had the money to do so.
That all being said I have seen the L-N-L in action and its also a great machine. Between everyone I know its about a 50/50 split over who uses what but those two companies own the market on progressive.