Well, I checked it out. You have three options -- promoting a single item, promoting up to 10 manually-chosen items or promoting search results for a specific term (no, an eBay ID doesn't work).
Boy, was I disappointed! I was completely surprised to learn that there's no option for simply promoting your latest listings based on your selling ID.
The closest option is promoting up to 10 manually-chosen items but Slide.com is already working quite well for me.