I have tried it. I prefer a beeper collar, but my dogs are never more than a couple hundred yards from me at any time. If you're hunting wide open areas and the dogs are ranging a half a mile or so away, this unit would be a great tool.
Here is a link to another discussion board (I assume it's ok to provide this link) that may give you some good info...
http://forum.versatiledogs.com/viewtopic.php?t=6272
Good luck