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.
Just installed this and already love it. Great add to Flickr. One thing I noticed - my landscape oriented photos are not resizing correctly so the right hand side of the photos are being slightly cropped. It is minor but it is noticeable especially in the uneven composition of some photos.
This Flickr Gallery Plus extension is a very nice first version. Flickr's photo set navigation always confused me a bit, mostly in its inability to give the user a clear overview of its current position within the set. This extension solves that nicely! The slideshow a nicely added touch.
One point of improvement I would like to suggest is reconsidering the inclusion of an icon in the status bar to enable or disable the functionality. I truly dislike extensions who needlessly put icons in my status bar (and even use the extension called Organize Statusbar to hide some of them).
Is there a possibility for you to include this toggle within the Flickr website itself, where it's relevant? This also improves its findability, as I had to read the author's document to figure out how this extension works exactly.