Ultra short throw (or UST) has been around for quite some time in the classroom space, however more recently this technology has been incorporated with the brighter, large venue projectors. Classroom UST projectors, as well as being limited in their brightness, are also limited by the size of the image they can produce.
NOTE: Chart above is indicative and actually for Z series product.
The main advantage to using a UST lense with lets say an Epson G6750W (6,000 ANSI) is that the projector can be mounted extremely close to the screen and still produce a huge image, without compromising the brightness or quality.
The lense shift functionality on the large venue projectors also allows them to be mounted higher than the image itself. This means that due to the sharp projection down angle, the bright light in the eyes of people on stage is reduced, if not eliminated. The shadows from presenter/performers on stage is also reduced dramatically, making these the perfect projectors to be used onto the cyclorama (white back-drop) in Drama/Theatre spaces.