Rated 3 out of 5 stars
The layout and usage reminds me of my SmugMug galleries, which I like. This is the way Flickr sets should have been made (one photo viewed large, switchable from the thumbnails). However, there are some serious issues with this add-on. For instance, if you have more than 40 or so images in a set, then you have to scroll back up to see which one is displayed larger, and the page takes a long time to load. Work on the pagination -- maybe 30-40 images per page -- and this will be a killer add-on.
Regarding the scrolling, I agree. However, some people find it annoying with "jumping" pages as well, so perhaps a setting?
With loading time, it is probably because you have preloading turned on, which will preload ALL large images. Turn that off and only the pictures requested by you at click will be loaded (this feature is rather to offer smooth slideshows and such, but generally works better with smaller sets).
Pagination could perhaps be added, but that would take a larger modification of the Flickr page, which I try to avoid to respect the original look of it.