I bought my 500R over from Sicily in 2003.
There was/still is lots of work that needed/still needs to be done to it. Regardless, I drive it everyday - it is my only working car!
It has been driving very well over the many years i have owned it, and I frequently take it on long (100 mile+) journeys, with only the usual easily fixed problems coming up.

A list of the modifications I have carried out so far (Pictures to follow):

•652 Engine with Polish wasted spark coil
•Abarth 4.5L Sump
•Black Cobra Classic seats with red piping and headrests
•Luisi solid Mahogony Wodd rim steering wheel (13")
•Lumenition 'optronix' Electronic ignition module
•Electric window washer pump 
•Dell'Orto FZD 32/28 Carb 
•Reground fast road camshaft by Kent Cams 
•Stainless steel single exit sports exhaust (CSC)
•Wooden Luisi 'Imola' 30" steering wheel (still to fit) 
•Disc Brakes (Fiat X19 calipers, modified 126 bis stub axles) 
Fiat 126 Bis rear brakes 
•Cromodora 5Jx13 alloys fitted with Pirelli 155x65 tyres 
•Up-rated Delphi gas front shocks
• Chrome Lucas wing mirrors (sitting in box still to fit)

All in all, it handles extremely well and is a reasonably quick and extremely fun drive.
The body work however leaves a lot to be desired, with a few rust spots and cracked/faded paint all round. One day I will get this fixed, but right now, I am enjoying driving it too much to take it off the road (plus the lack of time/funds to get the paint/body work sorted!).

As you can see from this picture, there are several body work issues that need addressing at some point. In this picture you can see where my car was nicely reshaped by an incompetent range rover driver. The large exhaust ensured that their car received some damage for the pleasure!

This is what it looks like now. I have taken the car on a nice long test drive, but it definitely still needs some fine tuning on the front end set-up.

In hindsight, I think I would've preferred to fit a set of slightly smaller tyres to the 155/65 R13 that I am using currently. It is just hard to find a set of 145/55s or 155/55s and they are very expensive, but I'm, sure they would greatly improve the handling.

I have since fitted a pair of Michelin 145x60 R13 tyres to the front wheels whilst retaining the Pirellis on the rear. It handles superbly now.