It works, it runs, it ruins any attempt at validation you have ever hoped for. My website went from 0 css errors to 38 (and that was being kind, I use CSS3, at css 2.1, which is still the defacto standard, there were 43)
Now I understand that basically no gallery plugin is going to validate, I have faced this and moved on, created a new footer with no valid css just for my galleries... BUT! This messes up EVERY SINGLE PAGE. Not just my pretty portfolio page, and don't get me wrong this plugin looks fantastic, but not fantastic enough to destroy the css on every page on my site.
Great looking plugin, now try looking into it a little more.