What is your % of really good photos?

It depends on you definition of "really good", of course.

I'm not completely rigorous about rating, and I have a lot of fire-away kids' sports shots, but LR right now has 25K photos, 1000 rated 3 stars or higher. I just created a photobook and only printed 40 that I considered worthy of publication.  I usually expect one or two outstanding shots out of any serious outing.