One week after my first 2-day KDP Select free promotion, and the numbers stand thus:

3471 free downloads in total (the numbers all the way on the right). Way more than I was expecting; definitely a good thing. Those numbers froze one week ago as soon as the promo ended. A DREAM OF WAKING was purchased 105 times since then with 1 refund (Amazon has a 1-click-purchase setup that allows you to buy without a confirmation. They offer accidental clickers a several-minute window to refund their incorrect purchase.), with 30% of the sales taking place the very first day after the promo ended. This was due to the book’s increased visibility on Amazon’s charts (boosted by the free downloads). 10 people lent DREAM to a friend (a definite bonus to the program—I don’t have to work for this number at all, it’s simply icing on the cake).
Sales slowed about mid-week down to 2-3 per day, until Saturday night when 6-7 were sold. Looks like there are more readers willing to scroll down the lists on Amazon over the weekend (DREAM slipped gradually during the week, from #1 in its category to somewhere in the mid-30s). As sales slow, your ranking drops.
Overall I got more out of the promo than I was expecting. I’ve already received several extremely helpful ratings from people I’ve never met that downloaded my books during the first promotion. I have my fingers crossed that more reviews will trickle in once people read ASHES. I wish DREAM and ASHES could trade places numbers-wise, but I’m still happy with the 500+ my first novel pulled in. I am running another free day just for ASHES at the end of the month (instead of for all four books) so I will have more time to devote to its promotion. Going into the free promo without any ratings on Amazon for a novel was not the best move (and I believe it was the reason it was left off the website where DREAM received most of its press), but now that I have a few I think it will look more appealing to readers (and website admins—some sites won’t post your book without ratings).
I’m working on another short story (first of a series, hopefully) and plan to release it just before the next free promo for ASHES begins. I’ve noticed that every successful writer taking advantage of Amazon’s KDP Select program has multiple works available, and I need to get my numbers up. If I can balance short story writing with releasing a novel every few months, I should be in good shape in a couple of years.