My speed/cadence sensor broke before christmas and I finally got round to ringing Garmin this morning. After pressing one number I got straight through to a call handler. Asked me a few questions, determined it was broken, and said there was no need to return it, they would just post a new one out to me. I emailed off my receipt and details, withing 20 minutes I had an email back confirming a new one would be with me in the next 10 days.
Well done Garmin.