Does the use of a clean, well-maintained room air conditioner (either
portable or window-installed) pose any documented risks to the health
of the room's occupant? (risks of colds, sore throat, stuffed nose,
etc)

Don't know about those but this side effect may interest you. 

--------------

From New Scientist
--------------

Air-con and lack of sleep promote obesity

    * 12:56 27 June 2006
    * NewScientist.com news service
    * Kurt Kleiner

Obesity is just as likely to be caused by lack of sleep and too much
air-conditioning as it is by a sedentary lifestyle and aggressive
marketing by the food industry, according to a research article that
challenges the conventional wisdom.

Read the article @

http://www.newscientist.com/article/dn9416-aircon-and-lack-of-sleep-promote-obesity.html

The key words are 'well maintained'. Most a/c units are not adequately
cleaned, and things like mold infections can make some folks really
sick.

Common sense tells me that dust the particles that usually settle on
furniture and everything else must be kept in circulation by air
conditioners thus leaving the particles airbourne and likely to be
inhaled , airbourne germs likewise . Documentary proof seems unlikely
as who would profit from the research .

In response to a previous posting:

The reason air conditioning is linked to obesity is because people
naturally have less appetite in warmer climate.  Heard that this past
week on NPR.