First, the free version of Picasa Web gets 1 GB of storage (up from 250 MB), enough to host 4000 high-quality photos. It's interesting that Google says "1 GB (and counting)" so the storage could increase like it does in Gmail.
Like in Flickr, you can also search the public photos posted by other people. Until today, you could search only your photos and the public photos uploaded by your contacts. Google wanted to be polite and ask you before including your public photos in the community search, so you must go to settings and enable this.
I told you last year that the new Blogger uses Picasa Web Albums to store photos. Now you automatically get new albums that store all the photos uploaded to your Blogger blogs. This is a nice way to view and search all the photos uploaded to your blogs, but also to backup your photos. For more context about a photo, click on the link to the post that includes it. Here's the album for Google Operating System.
It's also easier to link to a photo and you have more options when you embed a photo into your site. If you want even more options regarding the size of the embedded photo, check this post that lists all the available photo sizes.
{ Thank you, C. I. R. E. }