I own an Adam too. The Pixel Qi is quite usable outdoors, though not as high-contrast as old-fashioned paper (or, probably, e-ink). It's a light-gray rather than white background, and dark-gray rather than black text. But I've used it outdoors for up to half an hour and it's very comfortable.
Indoors, the backlight is required but I leave it permanently at the lowest setting (and I wish there was a still lower setting). It is much better than any LCD I've used.
As for the glossiness, that's why they ship a matte screen protector. Presumably it's not default because some people don't like matte.
For me, the Pixel Qi is the unique selling point of the Adam. (The hackability is the other big plus -- if you don't like their ROM, flash your own -- but it's not unique.)