The first generation Previa was the only one sold in the United States. Like most minivans of the time, the Previa only had one sliding door. It did have something that was fairly unique among minivans, a mid-engine platform. The I4 engine was mounted so far back it was almost below the front seats. The even weight distribution helps the Previa handle better than most minivans, and also gives it better ride quality, which can be a big selling point. The big drawback was that the platform could only fit a small I4 engine, which prevented the Previa from being upgraded into more powerful vehicles like most of its competition.
A supercharged version of the Previa's I4 engine was offered starting in 1994. That gave American buyers a little bit more of what they were looking for. It was so popular that the regular I4 engine was discontinued in 1996.
Some people are still importing the newer Previas into the United States, but they are running into some problems with the Department of Transportation and EPA officals.
Previas sold fairly well during their time in the United States, and they are not too hard to find on the used minivan market. If you are looking to buy one, the best deals you'll find are on eBay.