I found a good blog entry on Dryel and Dry Cleaner's Secret. I've always been a bit dubious of the cleaning abilities of these products. It makes sense to me that loose dirt would come off a garment in the dryer - and the airflow would certainly help freshen garments.
It's been recommended for a long time that garments be left to hang someplace with good airflow if they're to be worn several times between cleanings (especially good for things like coats that don’t pick up as much oil and perspiration from the body).
This freshening is a good idea if something has been worn lightly with little contact with the skin. It reduces the wear and tear of thorough cleaning, and helps keep odors from sinking into the fibers.
However, perspiration and oils from the skin are pernicious, and the longer they sit on a garment the more they sink in. These oils also attract bacteria that eat the oil and the fibers it sits in, which reduces the life of the garment too.
Still - I wasn’t sure. It’s possible method of bonding oils to a truly “dry” chemical was discovered. So I looked around for a second opinion. I found a few reviews that tended to confirm my understanding of how these products worked. This article seemed the most detailed on the subject, and also compared the two products - Dryel and Dry Cleaner's Secret to each other:
http://www.associatedcontent.com/article/729027/dry_cleaners_secret_vs_dryel_home_how.html?cat=46This paragraph that spoke most to my question about whether they really clean:
"For both products, the purpose is to freshen and lightly clean slightly soiled garments. Neither product is suited to do "heavy duty" dry cleaning of clothes. Instead, these two products can be used to freshen a garment to wear again without professional dry cleaning services for a period of time. After you wear an outfit on a particular day and you desire to wear the outfit again that evening the home dry cleaning kit is effective for refreshing the garment.” (pg 2)
-H