The magicjack is still working for me quite well. Once in a while when I pickup my phone to dial, I hear a dial tone, but when I start dialing, the system does not register my button presses and continue to give me a dial tone as a dial. So i unplug the magicjack's usb cable and reconnect, then all is ok again. i tend to have to do this maybe once or twice per month.
Again, here is my operating environment at my home:
Internet Service Provider: Cox Communications
Internet Speed Tester:
www.speedtest.netRated Download Speed: 30 mbps
Rated Upload Speed: 2.5mbps
Computer CPU Type: Intel Pentium 4 2.8 Ghz
System RAM Memory: 2GB
A couple months ago, i brought my magic jack to my brother's place, here were his operating environment for my magicjack:
Internet Service Provider: Cox Communications
Internet Speed Tester:
www.speedtest.netRated Download Speed: 1.6 mbps
Rated Upload Speed: 0.25 mbps (248kbps)
Computer CPU Type: AMD 1.0 Ghz
System RAM Memory: 0.76 GB (768MB)
the magic jack still worked ok there. I called my cellphone using the magic jack and had my cellphone call the magic jack and the sound was fine. Of course the sound is not super-100% crystal clear. It was like a cellphone reception and there was a split-second delay while talking back and forth.
So as long as your computer and your internet speed is between the test cases detailed above, then you should be fine. For $20/yr that's good enough for me.
To answer your final question, I current run my MagicJack is my only phone system at home. I do not have a wired/LAN line at all. I use my magicjack to talk to clients during my remote computer services appointments several times per day. And seems to work fine.
HOWEVER, I DO disable any current peer-to-peer downloads that I may be doing before using my MagicJack, as the sound does get choppy sometime if lots of data is downloading - like over 100 kbps i believe - though i haven't done precise testing on that end.