I wouldn't mind paying the MJ company $40 for unlimited service for the year if I could use a sip device as my perferred access technology. The USB only drawback is also what limits SKYPE's technology (and google's) from taking off even if it were free.. nobody wants to jump through "hacks" which jump from one service to forward to another to make it work.. just make it work with the one and they'll have volume of customers/subscribers, etc-- make it complicated and even if you give it away free, it can only fill a limited niche use.
Actually, MgicJack does use SIP. I'm using a softphone with it right now because the hardware device crapped out. It's rock-solid though DEFINITELY not supported by MJ.
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