I have the rock and roll. It is big and heavy, and is more like a permanent fixture in the basement as opposed to dragging it out when I need it. But its a very very stable platform.

The rocking isn't like the real thing, like they imply on the website videos. However, it does force you to ride smoothly, both from swaying and bouncing motions. I tried both the Road Machine and the Rock and Roll, and found the R&R much more comfortable to ride. The motion it provides also comes in handy when you do out-of-the-saddle sprinting/intervals. You can rock the bike a little without worrying about stressing out the frame.

I would recommend it to anyone considering a trainer.

I find the resistance heavier than actual road conditions. I can usually maintain 31-32 km/h on the road, whereas I'm in the 28-30 km/h range on the trainer. That's not necessarily a bad thing though.
I use it in conjunction with a couple of Spinervals DVD's....they're great, and will leave you wasted after the 60 mins. Other times, I just throw on a movie for 2 hours and spin.

Not sure if I'd be able to do that on the rollers.