Been looking for a good option for creating a remote control car but it seems Lego released an "official" way via the 9398 4X4 Crawler but it's expensive. How does it work? And that's really two questions . . the "how" as in the mechanical part and the "how" as in, does it feel like a regular remote control car? Supposedly there are a few new technic parts in this kit according to this site which I assume are to make it act like a regular remote control car.
You'll want to read the TechnicBricks review of that set, which is quite detailed.
In short, there are two new motor types; one of which is a servo motor used to control the direction. As the remote used is the usual on/off one, it means you'll be able to steer right or left, but with no granularity (you can also go straight ahead, of course). The other motor is a regular one, but again the lack of granularity on the remote means you can't modulate the speed of the car.
TechnicBricks also has an article dedicated to the two new motors themselves.
Having never really used remote controlled cars, I can't say how it compares to the real stuff. I suppose the lack of speed regulation can be a problem, but you should be able to build a better remote using the IR Speed Remote Control .
Edit: according to LEGO the new motors will not be available separately before march 2013, which I suppose means they will be available separately.
It is built like a regular RC car, there is a two channel remote and receiver combo with outputs for a motor channel and for a servo channel. The steering is done with two separate servos (S Motor, as Lego calls it), which are connected in parallel to the receiver.
The remote is a tiny two channel affair with two side-by-side levers that move front to back, like a tank control. One of these is (crudely) converted into a wheel type direction control, which you turn forward or backward for direction control.
The RC system uses infrared, not radio, so you will have to point the remote towards the vehicle.
This whole remote setup might be the biggest letdown with regard to the feel of a proper RC car. That, and maybe the performance of the drive motor.
As far as I know, the radio can be switched to four different channels.
I don't own the set, I just read the build instructions available at Lego
There is a video of the vehicle in action at Frequency. OMG! They puts the precious in the sand and waters!