Intermittent signal stuttering. Our test unit would occasionally lose sync with our Blu-ray player over HDMI, leading to a burst of static or a re-sync operation. This happened most often on static menu screens, like our Blu-ray player's startup screen or a static laptop screen. Rarely, if ever, did it occur during the viewing of actual content. Still, in light of this, it would be wise to use the shortest cables possible when running HDMI from your source to the projector.
Placement flexibility. With a 1.2:1 zoom lens and no lens shift, the H6500 is somewhat limited in where it can be placed. The projector has an upward throw angle offset of about 16%, meaning that the bottom edge of the projected image will appear 16% of the image's height above lens centerline. This is great for ceiling and coffee table placement, but eliminates rear shelf mounting as an option unless you're willing to apply keystone correction. This sort of lens is not unusual for inexpensive DLP projectors, but we've seen better before in products at the same price point.
Flimsy lens adjustments. The H6500 has a 1.2:1 manual zoom lens, which is not in itself a bad thing. However, the zoom and focus rings feel cheap and plasticky, and we found it hard to obtain precise focus on occasion. As the H6500 is a projector that is highly portable and likely to get moved around, this can be a hassle.
Dynamic black is slower than an iris. The H6500's dynamic lamp system, while effective in its efforts to optimize brightness and black level, is slower than an automatic iris. This isn't just an Acer problem; Optoma has been working on a similar technology for years and their implementation still is not as fast as a good auto-iris. What's more, the fan noise rises and falls as lamp power changes, so unless you're seated well away from the projector, the cycling can become annoying quickly.
Lackluster color adjustments. No projector looks perfect out of the box, not even the really expensive ones. However, with a full suite of color controls it is easy to correct for any flaws you find and bring your projector in line with the HD video standards. While the H6500 doesn't look terrible at defaults, its color controls are rudimentary enough that it is difficult to effect any kind of meaningful adjustment to the picture. The H6500 has adjustments for Red, Green, Blue, Cyan, Magenta, and Yellow - a single slider for each color, with no distinction between hue and saturation and (more importantly) no distinction between color temperature and color gamut. Trying to calibrate this projector quickly becomes an exercise in frustration, so it is easier to find a factory calibration that doesn't look half bad and run with it.