This update improves the addon very much. It's really nice now, even working for large galleries with ~ 100k images and comments. Already ready for default style, little styling tweaks in EXTRA.css will make it fit perfect for UI.X styles.
Looks as expected with Default style, other styles may need css adjustment. Reasonable features (such as option to switch off categories in side bar), seems to perform well even on a 70k images installation. Could be improved with some features, such a showing thumbs and comments for categories with sub categories. Price is a bargain for what it delivers already. Thanks!