I use it 6 or 7 times a week and it always works, although no necessarily first time. Sometimes it will fail on the first attempt but work on the second. Rarely is it worse than that.
If having pressed the back/forward button the steering wheel and dash don't respond immediately then it's not going to work. I immediately release the button and have to wait for 10/15 seconds while it sorts itself out and the greyed out back/forward enable again. On second press and hold, I find 9/10 times it works. In fact I used it today and a chap parking his car nearby had his jaw on the ground
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I've used it ever since getting the car (2.5 years) and it's arguably more reliable now than it used to be. I have found it works better if the phone has a cellular rather than a wi-fi connection.