My ad on The Romance Reviews has been displayed for three weeks, with one more week to go. It's a big ad along the left side of the site; grouped vertically with other covers which are all linked to their author's page (and where to buy), and the position changes frequently so sometimes mine is the first one. Unfortunately, so far this experiment with advertising has been pretty much a complete bust. Sales for Special Offers have not improved, in fact, they may be a bit slower this month.
The site itself might not be optimal for promoting the book; Special Offers is a paranormal romance-urban fantasy and the site seems to lean toward books that seem more romancey than mine. I guess a better description of my book is paranormal with elements of romance. There's no love-at-first-sight (although there is lust-at-first-sight) and the one reference to heaving breasts and throbbing members was purely sarcastic.
In case my cover art wasn't helping attract buyers on the site, I updated the it after an extremely talented illustrator gave me some pointers (Thanks Daniel! Check out his novella Dakota Rawhide - it's awesome). However, the cover art has been changed in most places the book is available for sale (the exceptions being the sites to which Smashwords sends books from their Premium Catalog, which won't be updated for another week or so). Therefore, any potential upswing in sales won't tell anything about the ad per se. If I had wanted to get a valid assessment of the site, I should have left the cover art as is until the ad ran out.
And, of course, perhaps ads of this sort are never particularly profitable. If anything improves in the next seven days, I'll let everyone know. But at this point, the bottom line is that advertising on that specific website has been seemingly unproductive.