I own a RM1x, and it is a great sequencer.
First off, the screen is nice and big, so you can see lots of information. The menu system is graphically done too, so you can scroll through menus, instead of having the options flash by your face.
There are three different ways to sequence too. You can sequence live, where you play the music into the machine live. You can step record, where the RM1x displays a grid on the screen and you punch in what notes go for what step. Then there is the X0X mode, where the mini keyboard turns into a 16step TR X0X style sequencer.
On top of that, you have different user banks to store and name your sequences. These are all easilly accessed from the instant you turn on the unit, simply by turning one of the knobs under the display. Now, each of your seqences is divided into 16 sub sequences. This is probobly one of the greatest features on the RM1x, because it allows you to rearrange your music in real time.
For instance, in sub sequence A, i can lay down some drums, a bass line, strings, and a piano, then I can copy all of these over to sub sequence B except for the strings. Then I can copy all of those over to sub sequence C, and change up the drums adding a fill. Now I can use A as my chorus B for somebody to flow to, and C for transitions.
THEN you can take all of these, and arrange them in the song editor. All you have to do is select what sequence you want to use, then arrange all the sub sequences in the order you like. ON TOP OF THAT you can even record live stuff into the song that wouldn't fit into the sequences!!! Like, yeah throw a piano solo in after 15 bars, but keep sequence B looping the background.
Then you can save it all to a disk!!! There are so many editing tools in this box too, its crazy. Wierd functions like Random PAN, where notes are randomly panned for a channel. Great onboard effects too, that are pretty much FULLY CUSTIMIZABLE!!! You can edit your reverbs, change the delay, etc, or edit your choruses, edit your distorion effects, edit your EQ effects, its nuts man.
The sounds on the RM1x are pretty decent too. They have some great basses, and the drums are alright too. Definately not totally synthy techno oriented, but rather techno, hiphop, dnb, pop, jazz, almost any modern music genre.
I'd recommend you go try it out someplace. Ask any Roland MC Groove box user how easy it is to sequence and do things on their unit, and they will tell you it is a pain.
Here are a few tracks I have sequenced using my RM1x.
(Deep Gangster Story Beat)
(Rap Instrumental #33 (Mellow))
http://www.soundclick.com/bands/1/xxn1927music.htm