I have a relatively large iPhoto library which has photos from the last 4 years in it.
Prior to 4.1/4.2.1, the screensaver would seize on one collection within the library and show a very limited selection of photos over and over again.
That is, it would behave like this (simplified only a little bit):
1 2 3 4 1 2 3 4 1 2 3 4
Certain photos would be displayed over and over again.
Now, I can see photos from every collection and I don't think I've see a repeat yet!

Prior to 4.1/4.2.1, the screensaver would seize on one collection within the library and show a very limited selection of photos over and over again.
That is, it would behave like this (simplified only a little bit):
1 2 3 4 1 2 3 4 1 2 3 4
Certain photos would be displayed over and over again.
Now, I can see photos from every collection and I don't think I've see a repeat yet!