It looks very similar to Verizon's version, which works extremely well. I personally prefer VoIP because it is more flexible and I have a very affordable carrier, but $20 per month beats cable VoIP or Vonage (except for international calls). It certainly beats a basic landline which costs $23 per month around here with no features (no long distance, no caller ID, etc... just a dialtone).
Since there is a battery backup, you can even stick one in some kind of case or bag along with a corded phone to re-create the bag phone experience, just to mess with people.
Also, this is much easier than VoIP for someone who is not technically inclined. If you have good wireless service, just plug it in and go. Of course, VoIP is easy to almost anyone here, but a lot of people are intimidated by the process for one reason or another.
The biggest drawback is that 911 is GPS based rather than a hard coded address. In many areas, GPS is close enough... it can be an issue in townhomes, condos, or apartments since while the address is known, the unit/apartment is not going to be obvious. This would also be an issue in office buildings but this product is intended for use at home and most businesses use a PBX of some sort connected to POTS, T1, VoIP, etc.
Despite this limitation, I'm not one to panic about 911 calls without POTS service. Remember, a POTS line can go down too... all it takes is some careless digging, a vehicle crash in the wrong area, etc. It can take a long time to fix too, depending on how many wires were cut. It's always good to have two methods for calling if you are worried about this. Ultimately some people are better off keeping a POTS line, and some people are OK with wireless only, multiple wireless carriers, VoIP + Wireless, etc. Most things in life pose risk of some sort. Most people drive (or ride buses, taxis, etc) despite the fact that a lot of people are killed or injured in accidents on the road.
Bars are not a true indication of signal strength or quality.