I have been using this for over a year now and find it to be spot on. Having just changed phones I emailed CamerAlert in the evening to change my details and the following morning it had been done. An excellent product with excellent back up.
What can I say, BRILLIANT! Warns of all mobile and fixed cameras including average speed cameras, is very accurate and will work in conjunction with an iPhone navigation app. Weekly database updates are prompted as you launch the app on the iPhone and downloading new data is quick and efficient over WiFi or 3G.