Still beta (you can easily get it from filehippo), but brings around some nice new features. I have been playing around with it a little bit, things i liked most:
* Photo Viewer is a real eye-candy, it replaces your default application for double click, it loads relatively fast, and has some nice user interaction features (try your scroll wheel on the image itself, and on the film band).
* Collage maker - it has a killer interface to create the photo pile of your wish, resize, rotate, move your images one by one.
* Quick filter by starred, uploaded photos, videos, or even photos with faces. It doesn't include yet the face recognition and tagging that is already available in picasaweb.
* Movie maker - it is not really a movie maker, more like a presentation maker, but still, it puts much more control in your hands than before.
* There are some improvements on image import, and web upload, i haven't tried these yet.
One bug i have already came through, that whenever i restart Picasa, it keeps refreshing the thumbnails of the same images i recently added.