I like it, personally. I like Picasa, too, for its ability to scroll forever: if I'm looking for a particular photo of mine, out of the couple thousand, I like to be able to just scroll a single page, rather than keep clicking links to new pages. So I like that change.
The wodging them all together, it doesn't bug me. It's the fashion now. But I noticed in my cover photo header some links: below my name on the left are "Photostream, Sets, Favorites, Edit" When I click Edit, I get the old layout, with lots of white space and smaller images (although still with the new header). I'm a Pro user, so I don't know if all accounts have this. But if you hate your new stream layout, see if you have that link.
When I clicked Edit and got the old layout, the old, "Did you know you can change the layout of this page?" link is there at the bottom, but clicking that link got me a 404. So this view may be going away, or it may just be in a sad state of semi-transition, who knows.
I'm mostly annoyed that it's not true infinite scrolling. Previously, I had ~140 pages of photos, now I have 25. So there's a lot more on each page, but really, when I'm on the computer, I'm nothing if not very lazy. Just let me keep flicking the touchpad and scroll scroll scroll...