When I got the car, the odometer wasn't working, so I don't know the real mileage of my Fox. Must be over 200000 kilometers :). I fixed it since then.
A little glitch I often observed on many Foxes: the speedometer needle tends to oscillate around the real speed. When rolling 90km/h, the needle is waving from 85 to 95. Mine is almost O.K., I have a 2-3km/h difference.
To this date, I only had "normal" part wear problems.
I changed the starter, alternator, front brakes and shocks absorbers and some exhaust tubing & muffler.
Oh, and a pair of headlights too. Not the most expensive parts around, and I have done most of the work by myself.
My Fox has a little bit of rust on the sides, result of snow & salt (and some careless previous owners), but it's only surface rust. It pierced only in 2 small places, but I fixed it (for now).
I check my oil regularly, since the car drinks about 1-2 pints (1 liter each) per month, depending of the use (city - freeway).
Now here's the biggest issue about my Fox: water (not much of it, but enough to dampen the trunk's floor mat) gets in the trunk. I don't know how it gets in there, (the seal looks flawless) but I guess it's due to a kind of condensation phenomena. It happens more often during Winter...
I'm very satisfied of the Volkswagen Fox. I didn't have many problems with it, and surely would have less if it had seen better maintenance before I've bought it.
Of course, it's not as quick as a Ferrari, but I once smoked a Mustang (OK, OK, a 1985 2.3 liter automatic one, but it's still a Mustang! :) ). It manages very well to follow and flow through the traffic. You can thank the Golf/Jetta 1.8L engine for this. It's the same engine, except there's some exhaust restriction on the Fox, to make it less powerful.
I feel really safe when driving my Fox, the handling is incredible for a car in this category and age. I personnally use Volkswagen aluminum wheels and 175/70R13 tires. I think stock tires were 155/70R13.
The seats are quite comfortable, but there's a lack of leg room in the rear places, which make it an inappropriate car if you have lots of friends on the basketball team. The dash switches works in some weird manner, it can take a while to get used to them. In my opinion, the meanest drawback of the interior is the lack of cup-holders. (And the beige color scheme, of course. :) )