The DR-55 was strangley similar to a couple of other basic analogue drum machines of the time (ie Soundmaster). It had almost same layout and sounds, but these seem to go for about half the price.
They both were quite limited but sounded good. I sold the DR-110 years ago because its lack of midi and it didn't fit in to the sort of music I was creating at the time. Wish I had it now though. The hats and snare on those things are just what I like at the moment. (Similar to KPR-77),
I haven't a clue on the more recent BOSS machines. There seems to be tons of them.
of the dr range the best ones are the alesis dm-5, the roland tr-707, roland r8, and the akai-mpc500
seriously the dr series are crap. they have a small cramped interface, tiny screens, and dinky pads. they don't even sound that good anyway especially for 80's drum sounds. the alesis is a good all rounder with trigger inputs, nice kits and sounds and a good price. the tr-707 has a lot in common with the 909 as far as the hats and claps and interface. the r8 has a lot of the dr series samples (or the reverse the dr series has some of the r8 set) a bigger interface and better pads and is cheaper. the akai mpc can have any drum sound you want to put in it and a killer sequencer and bigger pads than the dr series...