I love this plugin. It does an excellent job of truly selecting related posts, and increasing interaction with my site. Unfortunately, my server hates the plugin because it eats up too much memory. I don't think this is a YARPP issue; I think it's just a related posts-type issue, because of the need to query the server every time the post is loaded.
The only real alternative I'm aware of is to hard-code related posts into each post. But this would take me hours, because I would first have to figure out what is related. I'd love to see a dashboard-only version of this (or a dashboard-only setting), that would provide an in-between option. In the dashboard, when creating/editing a post, it would have the option to query for and select related posts. It would only do this once, at the time of publication, rather than every time the post is loaded. So there would be the advantage of the plugin's algorithms for figuring out what's related, as well as the advantage of "hard-coding" (sort of), in that it only needs to query once instead of on every page load. And, ideally, it would provide an option to go in to edit the post and re-query periodically, so that as new posts are added, there's the option to update the related posts setting.
Just a thought, as I don't see anything like this available anywhere.