Bought this for a home system where I was unhappy with the previous analogue line quality (I was using an Atcom IP02). Whilst this is expensive as a single FXO port for home use, it has performed perfectly. In particular, voice quality is good (I haven't had to change the default settings other than to set it to UK) and call construction/teardown seems reliable and quick (once I set the battery-reversal option correctly). What's more, I don't get any echo problems and I don't have a dependence on configuring a card in a PC.
Configuration can take a while to get your head around, but there are a few configuration examples available on the Internet. I have this connected to a PBXinaFlash system and communicating via SIP.
I've had a couple of questions about the firmware (mismatch between documentation and actual usage), and these have been handled by Voipon and ultimately Patton very professionally. Definitely a "good buy" assuming you are happy with a complex but very flexible configuration.