updated 02:40 am EDT, Sat October 30, 2010
Also features Ping summary and new controls
Apple has silently upgraded iTunes earlier today and restored the "Genius" features in a revamped fashion, renaming the sidebar (which became the "Ping" sidebar as of 10.0.1) to simply the "iTunes Sidebar." The new sidebar features Genius recommendations based on a selected song and even includes the ability to play samples of suggested songs without entering the iTunes store.
Members of Apple's ongoing Ping social service will also see a short summary of recent activity, but non-Ping members only see Genius recommendations, now delivered on-the-fly as songs are selected (they do not have to be played to generate recommendations). Ping members can "like" or post about a selected song, and all users can listen to recommended songs or sample albums right from the sidebar.
If no song is selected, the Genius feature recommends albums based on recent purchases or items in the user' iTunes Library. There is no new version number associated with this change, and of course the sidebar can be turned on or off at any time with a small control on the bottom-right corner of the main iTunes window.