You can use it for PhotoStream, Backup, Hopefully they'll come out with more functionality in the PC control panel soon. Personally I really like the nightly automatic backup.
Well I have a laptop PC and I installed the iCloud control panel and I can now edit my bookmarks on my iphone and have them automatically change in front of my own eyes in the Favorites folder on my PC. I find this immensely helpful in saving me time editing them twice on iphone and on my PC. I have only merged by bookmarks and nothing else.