First off, let me say that pretty much EVERYTHING that I fixed on the car was wrong with it THE DAY I BOUGHT IT.
As such, I paid a mere $400 CDN for a completely rust-free example.
Things I replaced:
Leaky brake distributor (ridiculously rare part, as it was only on the '87-'90 Fox wagons).
A bolt holding the alternator on was bent or backed out or something (can't remember); was an easy roadside temporary fix, then replaced the bolt and all was great... few bucks.
While I owned it:
Voltage regulator went out, so the alternator fed more volts than it was supposed to, so it blew my headlights... a new voltage regulator was like 20 bucks and a very easy fix.
It had a broken driver's side outer door handle (VWs are notorious for that) that I swore I'd replace and never got around to it.
This car was awesome... after owning two Fox coupes ('87 and '88), I REALLY wanted a wagon, so I went searching for months, 'till I found this diamond in the rough. After replacing the shocks and the brake distributor I just drove it. And drove it a LOT. My girlfriend and I lived 600 miles apart, and saw each other pretty much every weekend. I also drove it on countless roadtrips, etc.
After I sold it I found out that, though the odometer said around 230,000 km when I bought it, it had been rolled back and the real mileage was around 350,000.
Despite this, it ran like a charm and never needed anything other than routine maintenance. I also got decent gas mileage, averaging around 8L/100km on the highway and a little more in the city. It was comfortable to drive, it easily hauled all my stuff when I moved, and the back was big enough for me to sleep in or toss my mountain bike into.
It was reliable enough that, though it was nearly 20 years old with lots of kms on the clock, and I never thought twice about driving it 2,000 km in one weekend, and it never let me down.
I sold it to buy a 4x4 more suited to the Northern Canadian climate I had moved to, and have missed it ever since... and bought a Jetta GTX recently... old VWs are hard to beat ;)