I initially liked the new photostream layout, but after using the site for a little while, I think I prefer the old layout.
The new site definitely looks more modern and glossy, but there's a reason museums don't display photos in a huge mosaic -- it makes it very hard to focus on and consider one image at a time. Now to browse someone's photos I need to go into the "one image at a time" viewer, which takes longer and leaves a long browser history.
I'm not quite sure how I got to it, but go to user's stream and then tack on a ?details=1 to the end of the URL. I have no idea if that's an intentionally preserved view or not, but it's more like you're looking for.
The details=1 query string is added when you click "Edit" in your own photostream's header.
Funnily enough, at the moment the details=1 layout even preserves the old "Did you know you can change the layout of this page?" link at the bottom, linking to a 404.
The new site definitely looks more modern and glossy, but there's a reason museums don't display photos in a huge mosaic -- it makes it very hard to focus on and consider one image at a time. Now to browse someone's photos I need to go into the "one image at a time" viewer, which takes longer and leaves a long browser history.