I've had the Kurt Kinetic Rock & Roll for about a year now. It's frickin' awesome.
As a big guy with pretty strong legs, stationary trainer time is generally painful for me. If you know how your butt feels after doing a 40k time trial, riveted to the seat, add about 25 or 30% to that and you'll understand what my large butt feels like. Same size seat, bigger dude, pretty big power, greater PSI on the bottom. Add into this the crummy feel, squirming butt (from a completely motionless platform) and unnatural pedaling sensation of most trainers, and you'll know exactly how I felt before upgrading to this machine.
The Rock & Roll is based on the Kurt Pro Trainer. The guts of the trainer is a fluid resistance unit with a standard 6 pound flywheel, and an additional 12 pound flywheel that attaches easily with the help of a counter-threaded screw. The normal 6 pound trim is good for intervals that require snappy acceleration, spin ups, or 10 seconds on / 10 seconds off efforts. With the full 18 pounds screwed on, this trainer is much better for longer duration intervals and steady state training (zone 2, tempo, or threshold intervals). The bigger weight is harder to get up to speed and the tire will slip if you attempt to stomp and accelerate quickly. But once it is up to speed you will swear it feels just like the road. The big weights give this puppy a 25 or 30 second spindown from 20 MPH. In preventing instant sharp acceleration, they also mimic road feel. You can't go zero-to-25 in two seconds on the road; nor can you on this trainer. There is no resistance setting on this trainer. The fluid resistance unit is progressive, and I find I'm putting out close to threshold watts at 22 MPH, maybe three or five lower MPH than threshold on a dead calm day at Hains Point. The resistance unit is almost eerily quiet.
Even without the Rock & Roll base, The Pro Trainer is a great trainer. In fact it's the model I initially purchased last fall because it felt better than the comparable Cycleops model, at least to me. It's a top-of-the-line trainer, great for the serious amateur or a pro.
But it still isn't flexible. That's where the Rock & Roll base comes in. The Rock & Roll base is a flexible mounting bracket for the resistance unit, and it features extra-wide stabilizing arms to keep the trainer steady. Calling this base a "mounting bracket" doesn't do it justice. It is a stack of rubber cushions squished between a stack of steel plates that permit the trainer to rock side to side, forward & back a little bit, and up & down. Properly adjusted, it isn't bouncy or tippy, just mildly flexible in three dimensions.
What this means is that it is bloody comfortable to ride. It is the only trainer I've ever ridden that didn't cause my butt to start going numb within 5 minutes. In fact, it seems to be cushier on the hindquarters than the road itself is. I have ridden as long as two hours on this trainer without a break, punctuated only by an occasional (once every 20 minutes) standing spell. Other than the excruciating boredom - sorry, that's true and nothing gets you around it - nothing bothered me about riding this for that length of time. I use it with a Powertap and get tremendous workouts on this thing. It's possible to ride a workout that produces a power chart that looks like the wall of a castle - just these level, symmetrical square teeth representing intervals. You simply can't do that consistent of a workout outdoors. It's also harder to do on lesser trainers that break your will quicker than they break your legs.
It's also easy to snap your bike into and out of the trainer, and it's very well built, stout. You will want to use a heavy old skewer with rounded ends to fit it in tightly, but even so, it needed be as tight as a regular trainer because the skewer/trainer interface isn't under as much stress due to the thing's flexibility.
That stoutness comment brings up the Rock & Roll's only weak point. This human hamster wheel is big and heavy. It's about 34 inches wide, and about twice as long as a normal trainer. It has to be, because you're leaning and maybe bobbing a little (though the bobbing tends to encourage a smoother pedal stroke ad stops once you get your mind, and legs right). It probably weighs around 45 pounds. The stabilizing arms do disconnect easily making it much smaller, and dropping the primary unit's weight to perhaps 30 pounds, but this is the kind of trainer you can realistically only use where you have space for a full size set of rollers. It isn't really a viable option to take to races for warmups, though if you're the kind of person who warms up at races on your Kreitlers, you won't have a problem with it. I keep a cheap older Performance trainer around for that task.
If you are looking to do hard and/or long indoor workouts regularly, you should probably be in the market for E-Motion rollers, Kreitlers with resistance fans, or this trainer. At around $500, the Rock & Roll is a good competitive option, and possibly the most economical option among the three when you take into account bang-for-the-buck. The high end rollers are good options, mind you. Both of the premium roller sets offer have several resistance settings (in Kreitler's case by opening or closing fan doors), in addition to the progressive resistance provided by tire friction on the roller drums. The Kreitlers are wonderfully smooth traditional rollers, but they aren't cheap. When you start packing fans on them they get very bulky, and the price waves at the the $800 mark before passing it at pace. At the same time, Kreitler's standard rollers are not particularly forgiving of even minor flaws in the pedal stroke, so one would have to build up a good deal of roller riding skills in order to be able to do hard intervals on them. And forget about working on your sprint. The E-Motion rollers address this problem by putting the roller frame itself on another frame that allows the roller drums to slide forward and back. There are side bumpers on the E-Motion as well, which prevent slide-off. It's a great solution, and I understand the road feel is tremendous, and you can practice standing sprints on them withough needing superior roller skills. The E-Motion rollers, however, run approximately $300 to $400 more than the Kurt Rock & Roll trainer. Special bonus fact: If you already have a Kurt Pro Trainer, as of last year anyhow you could purchase the Rock & Roll base for it and retrofit the resistance unit. I'm not sure if other Kurt products can be retrofitted, but it would not surprise me.
The bottom line: If you're looking for a top of the line trainer for serious indoor quality time with your bike, the Kurt Rock & Roll is a viable alternative to the higher end rollers, and is probably a better value.