I had it working for about the last year until MagicJack (MJ) just implemented changes to their pbx servers as of June 9th. Now for the most part they are blocking anyone from using any IP PBX, etc. but their USB dongle. I'm hoping it's only a matter of time before hackers figure out just like the last few times. Also, MOH (music on hold) does not work with them; at least provided from your end. They have they're own which plays instead of yours when you put a call on hold. It's a loop of an instrumental version of Aerosmith's Dream On and a few other songs. I just got a Voicestick (VS) Next2Nothing (or whatever it was called) plan for my inbound callers and I use MJ for outbound. My MOH works with VS.
Only problem with the VS inbound calls is Axon doesn't handle the SIP headers and drops the call when I go to answer my extension with my softphone. (At least as of Axon version 2.01)