Putting Behringer in a rack always makes me feel a little dirty, but at ~$150, this was too hard to pass up.
I've only had it for a day, so I'm still a novice with it.
I put it in a nifty case with a Rossum Assimil8tor for voicing, and a Doepfer A-121-3 vcf to tame the output.
It's pretty nice. Well made, clean readable graphics, and I really like the feel of the buttons on the keypad.
Other vendors would be charging $500 (or more) for this hardware and feature set.

It's big in the rack at 52hp, but it also doesn't feel as cramped to work with like other complex modules.
The documentation is terrible, even for Behringer. There's a little "what", but there's not much "how".

But the thing I wanted to mention here is the often derided Musictribe app.
In this case, it's the RS-9's saving grace.
You can set the usual i/o things, but a second page let's you build and edit the patterns and steps,
and makes the module understandable for those like me that are just starting out with it.
The app's not pretty, but it gets the job done. I went from frustrated to smiling in about 5 minutes.

That's it for now. Recommended, especially at this price point.

noodlehut.bandcamp.com