I am still working on migrating my photos from Flickr to Google Picasa.
It has been a major mess. My mismanagement with my photos is the biggest problem. I never cared about creating sets on Flickr. I just uploaded photos as they were taken.
Flickr made it a mess by not offering an easy way to download your photos back. SocialFolders came handy. It is hard to be 100% sure but it probably downloaded everything on my Flickr account to my computer (except for videos I believe).
Google Picasa is very different from Flickr. While Flickr is based on linear uploads where you upload a bunch of photos and then decide what to do with them, Google prefers a traditional approach. You need to put the photos being uploaded in an existing or a new folder.
Flickr’s model is fantastic because you can have a single photo in multiple sets. And sets have no size limits.
Google’s model is horrible because you have to duplicate photos to have it in different folders. And even more sadness is that each folder can have a maximum of 1000 photos.
Google seems to be doing something interesting in Android Ice Cream Sandwich which lets me access my photos based on various parameters like Locations, Times, People and Tags. Some of these features were also introduced in Google Plus.
But it needs to do more.
I am also testing Everpix beta right now and I seem to like it a lot. From what I see, they have done it the right way. The service automatically categorizes your photos based on various parameters. It also seems to take care of duplicates. More features are likely to be added in the future.
I would love to have something like this on Google Photos which would eventually be the new brand name of Google Picasa. They need to remove the limitations. They have to make it fun to organize your images. They have to provide better handling of duplicate photos. They have to start treating photos as individual entities with support for multiple properties!