Roy, is there a way to tell if DSAs would work well for a given site?
Sure--try to set up a campaign. If the available Auto-Targets are too few, too general, or don't seem to successfully capture the spirit of your product catalog, then they're probably not going to work till you make your site a little more spider-friendly. If, however, a good chunk of your catalog's category structure appears available, then they're just another form of text ad, and the bidding logic is the same.
Have questions? Drop me a line via the Contact form--I love to talk shop.