The car has been extremely reliable but has some quirks.
(1) We have always had uneven tire wear on the front wheels and I know this is a problem other Previas have as well. This means that tires don't last as long as you expect them to (about 20K miles). I mean good tires, not cheapies.
(2) The shape of the car is distinctive, but makes it designed to be dinged. Look at most older Previas, you'll see what I mean.
(3) My 1991 Previa came out before the supercharge option and I wish it had a bit more power, but all in all, has done fine.
(4) My Previa came with a very high-end sound system (radio,cd,cassette, 9-speakers) and it has caught on fire twice. The first time Toyota replaced the entire unit. The second time they did not.
I have no idea why they stopped making them. It's been a great car and I would buy one again if I were in the market for a minivan. Good luck.

I couldn't resist putting in my two cents about the Toyota Previa. We bought a new Previa in 1992 and we LOVED that car. We maintained it well and it was abolutely reliable with not a single breakdown in 85K miles. We drove it all over the state fully loaded with baseball or volleyball teams and all their gear. It was never underpowered, and we drove onto a lot of freeways. The seating was extremely comfortable for long rides, with captain's chairs rather than a bench in the middle row and plenty of leg room for everyone. I can't speak to the comparison crash test cited by one of the parents, but I do think that the sides were reinforced. I always felt well-enclosed as opposed to Caravans we've ridden in. My one and only complaint was that the side windows in the second and third rows were not high enough for a tall person like me sitting straight up. I had to lean back slightly to feel that I had a good view of the outside. We sold the Previa earlier this year and got a smaller Toyota after our youngest went off to college, but there are times when I wish we still had that van.