I've owned my 2012 Fiat 500 for 3 years now and I have to say it's been a great little car. The fuel economy is excellent, averaging around 40mpg in city driving, and it's incredibly easy to park due to its compact size.
One thing that surprised me was how much space is actually available inside the cabin considering the car's small exterior dimensions. My partner is 6'1" and he fits comfortably behind my seat with plenty of legroom.
I've had a few issues with reliability but nothing major, just some minor electrical gremlins here and there. However, Fiat has been very good about responding to my concerns and providing software updates to fix the problems.
All in all I'd say it's definitely worth considering a used Fiat, especially if you're looking for something fun and fuel-efficient. Just be aware of potential reliability issues and do your research before purchasing!