I'm trying to get YARPP to work on pages as well as posts. I've got it working just fine on posts. On pages, however, it gives very sporadic results. Most pages show "no related posts" even though there clearly are common keywords. A few show one or two related posts. When I look at the yarpp_related_cache table, all of the pages that showed no related posts have an entry that shows an ID of 0 and a score of 0. I found I could override this by editing/inserting rows in the table and create related posts, but then any changes to any of those pages would cause YARPP to recalculate scores and go back to ID=0 and score=0.
I have the cross-relate posts and pages box checked. I replaced the one instance of "single" with "singular" in the include.php file to get related posts at the bottom of my pages.
I've noticed several others posting about difficulties with pages . . . but no resolution. Other than this issue, this is an awesome plugin!
Also, here's a feature request: I would love the ability to override the automatic choices and add my own relationships on some pages, the way Similar Posts did.