I did a lot of research before buying this. Jaspers produce the top keyboard stands and this one is quality and looks great.
The "R" stand has rollers or castors so is designed to be moved. Also, it is only 50cm deep as opposed to the 70cm depth of the A frames. It has to fit in the middle of the room which is not practical but being on castors means I can move it 2ft when not in use which is great. The 20cm saving is also a bonus in my small space.
The only potential downside is that if you push it from the back it has a tendency to tip forwards. I have it on a carpet which doesn't help but I'd still be careful if it was on a solid floor. It's just something you need to keep in mind when moving your £KKK's worth of gear :-)
When stationary, however, and when playing, it is very stable.
With all that said, it is still perfect for my space and I couldn't swap it for an A frame which, being static and with a larger footprint, will be more stable.
If your space is tight you could consider one of these and use it as a static rack.
I don't know of any other movable racks and I would still recommend this if you need one, as long as you take care when moving it.