Viewsonic is nice enough to serve up one of the best warranties available in the price range.
The Pro9000 projector comes with a three year parts and labor warranty. As an added bonus, for the first year, they offer a replacement program they call Express Exchange. Bottom line: During the first year, if there's a warranty issue, they will replace the projector (typically with a refurbished one - which is typical in the industry).
For the remaining two years, it's your standard, send it in to service warranty.
From a comparison standpoint, warranties with replacement programs are not very common. The Sony VPL-HW50ES, a more expensive projector, has three years with a 90 day exchange, and The Epson Pro Cinema 6020 shipping soon (also more money), is 3 years with a 3 year replacement. Epson's regular Home Cinema series come with two years with two years of replacement.
Most of the other players offer one or two year warranties. The Panasonic PT-AE8000 is one of those with a two year warranty. The BenQ W7000 offers just one year, as do most Optoma projectors.
In other words, there are a couple of projectors out there with as good, or even a slight bit better warranty, but most of the competition comes up short by comparison, to the Viewsonic Pro9000 projector's three year warranty.