1. As the article points out, most people drive less than 40 miles a day, and the Volt provided 40-50 miles of electric range.
2. Since the battery is relatively small for an EV, no expensive home charging system is needed - just plug it into a normal 120V outlet and it fully charged overnight.
3. Since it automatically switches to gas power when the battery discharges, there are basically none of the downsides of EVs. No range/charger anxiety, for occasional long trips I just use gas, and it's actually able to utilize a lot more of the battery because it doesn't need a "buffer" (i.e. for a fully electric car most folks are very wary to bring it below 20 miles of range or so). With my Volt a tank of gas would last me about 6 months unless I went on a road trip.
I wonder if, as pure EV sales slow down, that people and car manufacturers will start to see the benefits of plugin hybrids. I think if a plugin hybrid had better styling (as opposed to the Prius-derivative styling of most of them) that they would do a lot better.