I brought two of these controls and having read reviews on other website i was concerned they would not work together (as some people have said they work on the same frequency). I tried them out with my two offical controls and they worked fine! Obviously for the price the quality is not as good and they are lighter and more plasticy then the officials, but they work and thats the important thing.
The only real let down with them is the speakers are not so good, sometimes not much sound and crackles quite a bit.
Overall considering they are over £10 cheaper then the officials i think they do a perfect job as additional controls for friends and family!