This takes us to ergonomics, and that is the HD81's weakest area. Of all the 1080p projectors reviewed, this is the only one that lacks lens shift, which pretty much limits you to celing mounting the projector. Combine that with the short range of the zoom lens (1.2:1) and back wall mounting is extremely unlikely. That may cause a significant number of potential buyers to favor the BenQ W10000 or one of the LCD models. The LCD models have both vertical, and horizontal lens shift and lots of range in their zoom lenses (Panasonic PT-AE1000U 2:1, Mitsubishi HC5000 1.6:1). Then there is the minor annoyance that the HD81's lamp door for changing out the lamp, is on the bottom, so that if you are using a ceiling mount, you'll need to unmount the projector to change the lamp. Although this is pretty standard, on low cost projectors, the BenQ W10000, Panasonic and several other similarly priced projectors do not require umounting to change the lamp. While I'm picking on the HD81, I better mention again, the noise levels. At best, the HD81 is not a very quiet projector. It's noise level in low power mode is definitely acceptable, but noisier than the competition. In full power, however, it is noisy enough, that some people will be unhappy. This is one area where the BenQ W10000 has a big advantage, and the LCD projector competition - well, by comparison, they are dead silent!
While placing the projector in your room may be a challenge, interfacing it with the rest of your equipment is not. No other 1080p projector under $10,000 comes close to the input flexibility of the HD81 home theater projector, thanks to the extensive capabilities of the outboard Gennum processor box. First, of course, the box sits with the rest of your equipment, so only two cables get run to the projector (plus power). With 3 HDMI inputs (four counting the AV receiver option), 2 standard Component, and two more (BNC) inputs that can be used for component video or computer inputs, the HD81 is a class of one in input capability.
If you like to "play" with your projector, you'll simply love the HD81. It has extensive controls to adjust the image. The Panasonic is similar in that regard, (and has that slick waveform generator), but the Mitsubishi and BenQ just can't match the extensiveness of the HD81's image controls. (The BenQ has more controls available to an ISF calibrator than users can access, so from a pro calibration standpoint, it isn't really an issue. Again, however, if you like to tweak, adjust, tune - whatever you call it, the HD81 is a dream projector.
As I have mentioned, the HD81 is supposed to have an Anamorphic lens available for it, for those who want full Cinemascope (2.35:1) movie watching without the upper and lower letter box. For most people, that means a Cinemascope (extremely wide) screen, and probably a masking solution to reduce the width for HDTV, TV, etc. With that in mind, Optoma included fully programmable 12 volt triggers, so that you can control a masking screen. That's a feature not found on other competitors. (There are workarounds - a serious programmable remote, or room control system, can control an IR or RF equipped masking screen.