I purchased this unit when, dissatisfied with the value received from my local Bell company, I wanted to get more features and more power for less money using VOIP. Though I plan in the future to run my own Asterisk box, this is an excellent first step, as the device can be configured to work via IAX (which is the Asterisk protocol). This device appears to be the most widely supported - virtually all VOIP providers know how to set it up with their service.
After reading a few online reviews, I selected a highly rated provider who offered unlimited incoming calls for about $5 / month and outgoing calls for less than a penny / minute. Following their instructions, I was up and running in 5 minutes flat, placing my first phone call, and checking incoming calls with my existing landline. I will be porting my landline number shortly and give up Bell altogether.
The device sits behind my router with no performance degradation. There is no echo or clipping and the voice quality is excellent. It is best to keep the VOIP adapter separate from your router, as combo devices do not do routing well. Note however that you might be able to install Asterisk on such devices.
Though some providers offer this device claiming that it is unlocked, I prefer to buy it brand new (and obviously unlocked) and shop for VOIP service separately. I recommend this approach to anyone, whether it is VOIP or cell service you are shopping for.
This is an excellent device for VOIP first-timers. Note however that the unit does not support either the fax (T.38) or high-definition (G.722) voice codecs.