I've played with several VoIP appliances -- some thoughts...

MagicJack (original) - not usable for a home replacement as it needs to be connected to a working computer to operate.

MagicJack+ - Viable, Pros: you can port your existing phone number to it for a fee, supports 911 signalling. Cons: Draws power from a USB wall wart which is a bit of a loose connection, it's been reported that MJ has limited "free" calling to more expensive call locations like AK & HI. $30/year after first year but can buy 5 years for $100.

NetTalk Duo - Viable, bit pricey at $30/year after first year, can port existing #, e-911 friendly, but I had more problems than most with calls not going through or dropping.

Obi 100/110/220 - Can't port existing number and does not give 911 location but is still my favorite of the bunch, it uses Google Voice as the backbone for free (at least for the rest of the year, who knows in the future) and call quality has been good even internationally. Love that the voice mail can send you an e-mail with reasonably transcribed text along with an audio file (but can't confirm how well it'll do if you have a friend who speaks pidgin)

Ooma - Probably the best voice quality, but a pricey box -- I also have concerns that if they don't maintain sales growth they might be under financial pressure to stay afloat.

That said, based on your nick one thing you really have to check is that all these providers can give you an 808 area code as some don't offer them since it costs them more money.