It's one thing to buy service from a VoIP provider that gives you a router, usually now with WiFi, but if you're a serious VoIP user and want to pick and choose your SIP services the last thing you want is a locked VoIP phone that can be configured easily if it was unlocked.
PhoneBoy and VoIP Supply's Garrett Smith both are on the job telling the whats and the whys.
As someone who has invested in VoIP phones I'm amazed that more people aren't using them. I have one from Linksys and I connect it to my Gizmo account. All I'm missing is E911, something Mr. Blog has a perspective on, and why that may need to change.