No, not used one personally as thankfully I get very few spam calls. Any I do get are usually taken by my answer machine when I am out. Or if I do take the call, the few seconds of silence at the start of the call is a dead giveaway and I hang up before I hear the click of being connected to the next free agent.
However, I am from the same city (Swansea) as the manufacturer, and have seen them featured in the business section of the local rag recently singing its praises. Now, I am normally quite cynical when it comes to believing what I read in newspapers, but reviews on the net seem to back them up.
Take from that what you will, YMMV, etc.
