As a family of four, my wife is the main driver of the car, using it for the usual school runs and all other family journeys.(I hasten to add that we car share with our neighbour who has 2 children and occasionally another neighbours child, so generally the car has 5+ passengers for the school runs)
We bought the Sharan privately, second hand in 2002 with it having done 75000 miles with 2 previous owners to us. The car had a full service history and looked in good condition, it was the Carat version which was what we wanted (Alloy wheels, climate control, captains seats at the front, and a useful trip computer which generally reports of around 30 mpg for the school runs up to 46 mpg on the long runs). The car seemed to have had some small previous faults explained to us by the owner, such as rear windows not working due to a faulty door wiring loom, which he had corrected and the odd lamp or two not working, also corrected.
During our ownership, we have only had 2 bad problems, 1 of which was an engine restraining bar which sheared, (my local mechanic was of the opinion that it must have been fitted incorrectly at some point) causing a nasty noise under acceleration. The other is the air conditioning, estimated repair cost of £1200.00 from dealer, less elsewhere, but it means we have had no air con for a couple of years now... also the nearside door mirror has been hit (easily done these days) and the electric adjustment no longer works correctly, another fairly expensive repair.
As for the interior, most reports are the same, the plastic is very easily broken which is true. Most of our speaker grilles are cracked/broken, and the rubber seals around the rear doors are easily damaged as the children tend to slide in and out of the car, sliding doors would have also been nice. It is not very easy to remove the seats from the car and with it having not a lot of boot space it is fairly necessary to be able to remove them when needed, maybe this is something that has been addressed in newer models.
If you suffer from poor radio reception as we did, it is probably because it uses an aerial in the rear quarter light window, we had to get an electrical device to amplify the signal, now its fine.
Overall though it has been reliable, we are now up to 110,000 miles , still servicing yearly with VW with no other problems as far as reliability goes although, the starter motor is just starting to make the occasional funny noise on start up).
Having driven other diesels through work, the 90 bhp sharan does suffer a bit with speed/acceleration, the newer engines have I think improved this though. I hope that this is helpful.