HD1000U Lens Throw, Lens Shift, and Sharpness
The Mitsubishi HD1000U home theater projector shares the same placement measurements as the HC3000. To fill a 100" diagonal, the HD1000U can be as close as 11 feet 11 inches, or as far back as 14 feet 6 inches. This will allow some to mount on the shelf in the back of their rooms. Remember you are measuring to the front of the lens. So, with a shelf that is 24 inches deep, you are looking at a 100" screen working in a room 16.5 feet deep, and, considering the HD1000U has plenty of power, the popular 110" diagonal screen size will work shelf mounting in an 18 foot deep room. I wouldn't be afraid to match this Mitsubishi projector with even a slightly larger screen, if that works in your room.
The HD1000U does not have adjustable lens shift, and like its big brother, the HC3000 or, for that matter, Optoma's HD72, it has a lot of lens shift built in. This places the projector below the screen surface - or above. For a 100" screen, it works out to placing the lens about 16.9 inches below (or if the projector is inverted) above, the respective bottom or top of the screen surface. If you choose to shelf mount, you'll probably want it up high so people aren't walking through the image. You could mount it to the bottom of a high shelf, or use a shelf and build a simple cradle for it - to hold it upside down. If you try that, you'll want to make sure you don't do anything to limit ventilation.
As to sharpness, the Mitsubishi is pretty good, I would give it a very slight edge over the average DLP projector, and even a tiny bit more, compared to the Panasonic, but all would be very close, until you get into the few projectors (rarely in this price range) that have superior optics and sharpness. The Sanyo Z4 LCD home theater projector was especially sharp, and the BenQ PE7700 close to it. I would expect the new Sanyo PLV-Z5, scheduled to ship in November, to likely be sharper, but overall, the HD1000U does a good job.