Verdict:
It's a nice, light, quiet, and inexpensive keyboard.
But a defect with the Enter key on the keyboard I got makes it fairly unusable for me. I am returning it for a different model, rather than risking getting an exact replacement which might have the same problem.
The end portion of the video compares the loudness/quietness of typing on this keyboard compared to a laptop and a standard keyboard.
2013/10/13 UPDATE: I returned the defective keyboard and ended up buying another one of the same model, as I really liked it except for the defective key. The Enter key on the new one worked fine, but unfortunately the new keyboard had a different defect. The period (.) key didn't work unless pressed very hard. The Alt key also sometimes didn't work. As I got 2 bad keyboards in a row, I would advise against this model.
I have also tried out a different SIIG model - JK-US0412-S1. That one is more expensive, and the one I got does not have any defects. It is fairly quiet, but seems somewhat louder than the JK-US0612-S1. Key-presses on the US0612 sound thuddy, whereas on the US0412, they sound higher-pitched and "clickier". I'm not sure why, but typing on the US0412 doesn't feel as good to me, particularly when I happen to hit keys with fingernails rather than fingertips.