I've had the DR-110 and DR-55.
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.