I have one, the angelsounds from eBay.
Same as everyone else, my boyfriend was quite against it. I would get upset in the early stages as I had no way of knowing if my baby was ok, it's my 1st pregnancy, I didn't have a clue what to expect. We made a joke about it an he said he'd hide it and only let me listen if I was good. I think we must of used it about twice a week. Always a sunday night, as that's out day togther and we always got cosy in bed and had a listen.
Iv never not found the heartbeat, or always heard something
and the reassurance has been priceless! I only listen for a couple of minutes. It's been really interesting to see the different places you pick up the heartbeat and where the baby is lying. There have been some days iv not felt as much movement, and rather than get myself into a panic iv got the Doppler out and had a wee listen, and can usually tell the heartbeats a bit further back, baby must have moved!
I'm 33weeks now, and used it once last week when baby was having a sleepy day...
And also my boyfriend hasn't been able to make any of my midwife appointments, so hadn't heard the heartbeat. So it's nice for him to have had a chance to hear it.
Anyway sorry for the long post... My positive Doppler story... Best £20 of my pregnancy!