I have had majic jack for two years, its not perfect but for ten dollars a month its hard to complain. you can pick your number if its not taken. we had to get a new router to to keep from dropping calls, don't ask me why but the new router solved the problem we were having.
I had one for a year, no major complaints. Used it to talk to a couple friends so I didn't burn up my cell phone minutes. Now have unlimited cell minutes, so I don't have the magic jack anymore.
One thing that I found is that if you are making a phone call, you really can't do anything else on the internet connecting at the same time, or it will make the connection very choppy. Maybe not an issue with higher end internet connections, but my issue was with std roadrunner.