We've owned our 500L for 14 months and put 25,000 miles on it in a mix of city, suburban, highway driving and long trips. We've really enjoyed the car; plenty of passenger space, enough cargo space, excellent power and good handling. The visibilty is excellent - the split front pillars and tall side windows are great. Mileage, even loaded, has been very good and as expected.
We've had none of the little reliability problems early owners seem to have suffered. The car has never required service. The dual-clutch transmission does shift differently than a regular automatic, and occasionally a low-speed shift is not as smooth as the rest. And a couple of times when the car was cold it paused for a split second when taking off at a stop light.
If we could change anything about the car it would be a toss up between slightly heavier steering or deeper cushioned seats. The steering has good feel, but is light. Fiat did a better job on the Abarth, which uses the same system. And the seats are fine for long trips, but a bit more side support would be nice.
But where the car excels is that every time we get out of it we smile. Its a fun car. And there are so few cars today that make you feel that way.