I have one and I love it. I was not able to find the heartbeat till just before 11 weeks. It takes some patience to find it, so don't freak if you can't. After finding it the first time, some days I would find it in a second, some days it took me forever.
I also agree with Wobbles about the digital readout. A lot of times, I can hear the heartbeat, but it does not register. Honestly, as long as I hear that little thump-thump, I don't care. It is sooo freaking awesome hearing it. I also love being able to let my parents hear the heartbeat. They get such a kick out of it. What is also cool is the baby's heartbeat now response to us when we talk to it. Last night the heart beat was sitting at around 150, and I started talking loudly, and it went up to about 160, then back down when I stopped. It does it anytime someone talks to my belly now.
I was the one who took Wobbles advice on where to find the heatbeat, it was waaaay lower than I expected it to be. It was just above my hair line and just to the right. Even now it is still only about an inch above the line.