I don't see the problem - I used my 911SC as my daily driver for 3
years, and my 944 has been one ever since I bought it (better heat and
AC, better gas mileage). Maintenance isn't that bad, and the pleasure
in driving them is worth it.
    Emanuel

I have a 1987 924S with 192,000 miles (250K KM?) and drive about 40+ miles
per day in city.  As long as the car is regularly serviced, I see no problem
with using a Porsche (what ever model you choose) as a daily commuter.

On a good day I'll put 100 miles on my 1986 Porsche 944, drive it almost
everyday off the week year round. The reliability of the car is absolutely
amazing (knock of wood). I  get paranoid about the timing belt/water pump
between if it hasn't been done for a few years, but thats about all. If your
looking for a 911 as a commuter car, most owners will tell you the same
thing....they are known to be even more durable than the 944, depending on
the model.