I have a Punto Evo Sporting (135) that I've owned for 2 years and absolutely love it. I do 8000 miles a year in it, with a few 400 mile round trips in the summer, and the car has handled it with ease. No squeaks, no rattles, well built solid little car.
I also went on a six week, 4500 mile road trip around Europe in my mates sporting and it never put a foot wrong, averaging 45mpg with 3 lads, and a boot and back seat of camping equipment!
I know some people have had issues with their multiair units, but mine and my mates have been fine. I would advice you buy a car with full service history with oil and filter changes every year to be on the safe side.
Only issue I had with mine was with the blue and me system which cost me £270 to replace after haggling with the dealer. Wouldn't play music when I plugged my iPod in and had the odometer flashing. To be on the safe side my iPod only has 3.5gb of songs on it, as I was told Fiat recommend a USB drive of 4gb max, otherwise there's the risk the system will crash, which is what happened to mine.
Overall fantastic car that I won't be selling for a long time. Just make sure you go for one that has been looked after. I've looked after mine and it has looked after me. Also have a look at the government mot website. Theres a few sportings for sale at the mo, and a few have a whole list of advisories that need doing to them so watch out.