We really liked the Mitsubishi, and gave it our Hot Product Award, too. I'd have to say that, some differences in features and warranty, notwithstanding, the Optoma delivers more bang for your buck. (The Mitsubishi offers a three year warranty with overnight replacement) - I'd put a value of about $300 on that far better warranty, but that still makes the Optoma a better value, all else considered - it's brighter and still less expensive.
As a bright widescreen projector for home use, or other applications where movie or HD viewing is the norm, not data, the Optoma EP1690 provides the brightest image your under $2000 budget can buy. The EP1690 produces an excellent image in its best mode, where it is similar in brightness to the brighter home theater projectors. Its strength, though, is doubling or tripling the brightness of most home theater projectors, at the sacrifice of contrast, black levels and shadow detail. I can say that I dream of being able to crank up my BenQ PE8720 HT projector, when watching sports, but, of course, even in its brightest mode, it has less than half the lumens of the Optoma. As I pointed out in the Image Quality section, shadow detail and black levels are going to go down he tubes regardless, when you have a fair amount of ambient light, so the issue comes down to other areas of performance. With almost 2000 usable lumens, in brightest mode, the Optoma produces similar brightness to typical 4:3 business type projectors that are widely used in homes by those that need "more horsepower", but sell for a few hundred dollars less. The real benefit here, compared to those business projectors is the widescreen aspect of the EP1690 which means it offers true HD (1280x720) resolution, whereas those 4:3 aspect ratio business projectors are XGA (1024x768) and they can therefore only do a maximum widescreen resolution of 1024x576.
Translated, this widescreen Optoma has about 60% more pixels in use when viewing a movie - you simply have a much higher resolution image!!!
Comparing the EP1690 to its dedicated home theater sibling, the HD72, the EP1690 can certainly churn out more lumens than needed, but the HD72 has the advantage when the room is dark. Both have similar lumens in that case, but the black levels and shadow detail of the HD72 are superior. There is also the matter of the color wheel, only a 2X on the EP1690 vs 4X on the HD72, so there will be more people sensitive to the Rainbow Effect, when viewing the EP1690 (as would be true of other business projectors). Rainbow Effect notwithstanding, choose the EP1690 if you have an ambient light problem and also, perhaps, if your primary viewing is sports, gaming, etc., and you don't want to be in the dark.
Comparing the EP1690 to the Mitsubishi HD4000, in best modes, the Mitsubishi offers blacker blacks and more shadow detail. On the other hand, the EP1690 is simply a step up in brightness in all modes, and costs less.