Interested provided a very detailed review, I agree. However my experiences, based on riding every workday for nearly five years and over 12,000 miles (20,000 km) could not be more different. This involves a heavy salt/sand environment in the winter. In the summer, I tow my child to day camp with it. I have a Nexus-7 with roillerbrake.

Before getting my bike, I commuted for three years on the same route, under the same conditions, with a derailleur bike. I did not find the derailleur the least bit convenient or reliable. In fact, it made me think of driving a 1910 car with manual spark advance and an exposed chain drive. I'd routinely have just half of my gears available. One time, the whole rear derailleur came apart, scattering small pieces in all directions. Meanwhile, the rim brakes would reliably destroy the time, requireing a new wheel at the end of each winter. It was like using a violin to drive nails.

Some points:

The twist grip shifter is a drawback, especially in the rain and after the grip ridges have worn down.

Flat tire? Call a cab, take it to the shop. I'm not going to get my hands dirty on the way to work.

Preventative maintenance? change the grease and replace the shifter cable once a year. Costs about $30 at my LBS.

Weight? Who cares? Most bikes these days are too light and fragile for routine use.

Expense? Who cares? If I drove to work every day, it would cost me about $2,000 in parking.

I have the same expectations for my bike and my Mercedes -- no fiddling, no changing clothing in order to use it, no pieces falling of. Internal gears are required to accomplish this.

Paul