Now that I have Library Extension, I'm not sure I can function without it. It works great and saves me tons of dough on books.
I'd love to see Carnegie Library and state university library catalogs among those available in the extension, but Idk if those are available publicly in the way that the currently included library catalogs are, so it may not be possible (yet) to include them. Other than that tiny nitpick, this is a fantastic extension and I highly recommend it.