I'm asking this question because before purchasing my current trekking bike, a friend who owned a LBS was keen on selling me an Electra Townie 3i (2011 model) as a commuter (keep in mind that my commute is around 15-20 miles max both ways).

I have an Electra Townie3, and I do sometimes use it to commute 7+ miles to work, one way. But if I were going to buy one bike for the purpose of commuting it would not be this one. The upright riding position is not at all aerodynamic. The seat is too big and soft to spend much time on the bike. Out of necessity for a 3 speed, the gears are too far apart. This is a good bike for short trips to run errands.

Thanks for your input CR! Those were my worries, along with the placement of panniers and how nimble a bike like the townie can be in traffic with such a laid-back riding position.

Panniers are as easy as with any other bike. Of course the geometry of a Townie being what it is requires the use of Townie's proprietary rear rack. It's not a nimble bike at all, but it is a very stable bike that's fun to ride. It's just not a bike that I would seriously consider for a dedicated commuter.