I've got two 550's set up and running. There is a spare parts kit for the press available. Some of the plastic ends for the priming system will wear out over time. With some on hands experience the machine is generally trouble free.

You have good support on the machine. If you have problems the phone support is excellent. The no BS warranty is no BS. The last I talked to a rep had to do with getting a box of miscellaneous die parts put together. Rep talked me through it. The experience here has been universally positive then some. Right on the Dillon website.