Ive gotta say DP4 feels like something thats stable enough to ship. The only bug Ive encountered in 2 days of use was minor misalignment of desktop icons after exiting Safaris fullscreen mode.
Of course, installing the iCloud add-on is a whole other story. Things are a bit buggy because Apples servers havent fully migrated from MobileMe yet. Mail constantly crashes when trying to sync with the @me.com email account I created from the iCloud setup pane in System Preferences. Also, needless to say, even though I managed to get an @me.com account, MobileMe.com is limited only to using Find My iPhone because I dont have a normal paid account. Once iCloud goes public, everything should be fine.
P.S. Assuming the new Andromeda Galaxy wallpaper is the official default Lion desktop, I cannot say Im too happy with it. Its a bit distracting because of the contrast of colors, especially near the center. Oh well...