I'm with you in that it's strange that Apple don't really seem to have managed to come up with a solution for keeping photo libraries in sync. Photostream is a great way to pool recent photographs so that they're available on any device. For example, after a weekend away over Easter, I downloaded the photographs I took on my digital camera into iPhoto, and was then able to use Photostream to add some of the better pictures I took with my iPhone to the same event in my iPhoto library. The photos from my digital camera where then added to iPhoto, meaning that I could save my favourite pictures to the Cameral Roll on my phone.
So Apple seem to have done a reasonable job of pooling photographs (so that your recent photographs are device agnostic, and are available for import onto your phone, iPad, computer, etc.). With the galleries feature in the iOS edition of iPhoto (which we might hope will come to the OS X version as well), there is also now a way of sharing pictures. What's lacking is keeping libraries in sync. I want my iPhoto library, which is on my iMac, to be available on my laptop, and if I had an iPad I'd want it to be at least browsable on that. It's this feature that is arguable the most useful (I could suffer emailing iPhone pictures to myself to add them to my iPhoto library, and I think Facebook is a better way of sharing photos than the new galleries), and which is most conspicuously missing in the iCloud feature-set.
