The HD20 is a bit dissapointing in brightness, but not in a serious way. It's not based on our measurements, as the HD20 is brighter than most in best mode (Cinema), including most more expensive projectors, and about average in its brightest (Bright) mode.
The dissapointment comes from the Optoma claim of 1700 lumens. Now, most companies tend to overstate their brightness, and often significantly. That said, let's say that Optoma may have gotten a bit carried away, since it measured almost 40% less than their claim. (15% - 25% isn't that unusual, and it's rather uncommon to find a projector that beats its marketing claim).
Ultimately, though, we measured an impressive 701 lumens in our calibrated Cinema mode (User mode). Bright mode, measured 996 lumens (with just minor adjustments). Both numbers are post calibration measurements. Actually, using out of the box settings, Cinema mode was dimmer, though insignificantly, at 695 lumens