I've got a Clifford G5 on the cossie and it's been faultless. I've also got a Cobra on the Focus and have had no problems with that either. I'd happily recommend both. Best bit with the Clifford is the anti-hijack (BlackJax) which is part of the alarm. I've seen anti-hijack's sell as add on's for almost as much as I paid for the whole alarm.

I agree with the above though that the alarm isn't the most important thing, it's the quality of the fitting. I had a Clifford alarm fitted badly on my old XR3i which ended up having to be stripped out and re-fitted again.