Well, I've had my phone line running on MJ+ for a couple of days.
The voice quality is not delectably different either sending or receiving calls. When I called myself on my original line there is a time delay but I don't think it would be noticeable when there is no reference.
Hardware is what looks to be a USB thumb drive with two ports in the back (a telephone jack and an Ethernet jack). Also supplied is a power plug that the USB plug plugs into and a small Ethernet cable. I plugged My wireless phone into the phone jack, I plugged an Ethernet cable into the Ethernet jack and into an Ethernet switch that was connected to my internet router.
The online setup process is relatively painless, however you do need a computer with a USB port and internet access to set it up. You will plug in the MJ+ into your computer's USB port and it is is recognized as an extra HD (I didn't have auto-run configured otherwise it would just run the software directly). I looked at the drive and ran the software contained which then downloaded, off the internet, the most current version and started it. I clicked register, answered some questions (mostly asking to sell more services) and was given a phone number.
I unplugged the MJ+ from the computer, plugged it into the power plug which was plugged into a wall socket. The Ethernet cable and phone was still plugged in, so the little blue light comes on and it gets a DHCP IP address from the router and you are done. Picked up the phone and there is a dial tone. Called my old number and talked to myself. Using my old phone and dialed the MJ+ number and talked to myself. Called my MJ+ number from the MJ+ connected phone and you'll get lots voice-mail options to configure. Called others from the MJ+ line and had others call me, no one noticed a quality problem.
One thing to note is that the MJ+ transfers to its voice mail after four rings and does not seem to be configurable. I find that to be quite annoying for I don't want to use its voice mail but rather the answering machine built into my phone because it beeps. So I have to configure the answering machine to go off at 3 rings except it won't work on odd numbers so it has to be setup at two which is too quick. I'm not sure what I'll do about this issue.
Next is that because there is an ethernet port on the MJ+, there is no room for a telephone line splitter to be plugged in directly. I wanted to plug my fax machine in so it was necessary to use a small piece of telephone cord and a gender changer to plug the splitter into. I haven't yet tested my fax machine in that the faxback service I used to use for testing was discontinued and I've not needed to fax anyone yet. So that is yet to be tested. I know that connecting faxes to VOIP is generally problematic and if it doesn't work, I'll understand and deal.
Now that I have it working, I went to my.magicJack.com and transfered my landline phone number. It costs $20 and requires you to pick your telephone provider from a drop down list. Even limiting myself to CenturyTel (Quest), there are lots of choices. I have no idea which one so I pick the one in my state. 3 days later, I get an Email telling me the number has successfully transferred, so I guess I picked right. I have no idea what happens if I pick wrong (do I get my money back and pick again?) or if my old telephone provider isn't on the list. I assume that those issues are for tech support.
I didn't have to use tech support but from what I can tell from internet postings it's really bad so it is good that I didn't have to use it.
My conclusion: So far, so good I don't have any show stoppers. I've only tested this a few days, and I still have questions. Am I going to be listed in the local phone book and if not, can I manually insert my number by calling them? Faxing? Answering machines/voice mail? I'm willing to deal with the issues I've had for the money savings. Going from $45/month plus long distance fees to $30/year ($2.50/month) with no long distance fees for US & Canada is definitely worth the limitations.