In my experiance, the MK4 was the worse built car out of the MK1-MK5.
Had a couple of MK4's, low mileage and just shocking electrics etc. The MK5 seemed a little better built but even so, 57 plate with barely any miles and needs a new ABS pump.

Have to say, the MK3 seemed the last of the "solid" built VW's. But then, that's the same with every manufacturer IMO, all gone too "buy them, use them for a few years then scrap em".