I walked into an office that was using one of these.
Had to install a Juniper SRX100H behind their UTM for a VPN and setup two WAPs.
Got done, went on my merry way.
Next day: OMFG PHONES OUT BLAH BLAH BLAH.
After an hour onsite, found that when the VPN was up, the phones would go out. But only if the VPN was active.
Odd thing is, this little phone box thingy was plugged straight into the UTM, not behind the Juniper at all. But when the VPN was established the phones would drop out.
Code:
UTM-------------------
| |
| Ooma
Juniper | |
| Phones
Switch
| | |
Office Computers
Ooma support was less than helpful... even when I could understand what they were saying. ("What is jupiter sir?")

Ended up moving this thing over to their back DSL line.
Still never figured out what the problem was. This thing is like an expensive magic jack to me.