I use VOIP.MS for most services. Callcentric also offers some of the same, but I like Voip.ms better.
The Obi phones like the 2182 are more business phones and I sometimes see them for $55 but now people are charging $100+ probably because theyare being discontinued. HP more than likely bought Polycom to use the technology for HPs call centers.
Obi residential devices also were the only devices which integrated directly to Google Voices free telephone service (having a physical device that directly made and received Google Voice calls as though Google was a phone provider). That option may be disabled in the future if HP decided not to continue it. Still the devices still work with many, many SIP VOIP providers.