I second Kam05's post, I bought a replacement for my last IS and used it all the time and kept the original as the spare, never faulted the replacement, for my current IS I bought a 3 and a 2 button and again both are fine, one was from uk and one from over seas, and that one took aaaaaaages to arrive
now programming took me a couple of attempts, but I did get there in the end, so if you follow one of the online guides and it doesn't work, try again :D