The latest version of iTunes seems to have done away with a feature that many people have come to use regularly: the Genius sidebar. Instead of a Genius sidebar with options for finding new songs based on the ones in your library, there is now a Ping sidebar that gives you access to the social network's ratings and purchasing options.
This may be useful for Ping users, but the Genius sidebar was used by many to quickly find new song and artist recommendations and may be frustrated by its absence. The only Genius feature still remaining in the iTunes program is the ability to create playlists based on the songs in your current library.
Oddly, despite the Genius sidebar being gone, there is an indication that this may be an oversight instead of a replacement. For one, even though it is called the "Ping" sidebar, it is opened by clicking the "Genius" option in the "Genius" section in iTunes. Additionally, Apple's Web site still advertises the Genius Sidebar as being a feature in iTunes 10.
Perhaps this "replacement" is just an error where Apple forgot to include an option for the Genius sidebar, but we will see. So far there have not been any workarounds uncovered to either revert the change in the program, but they may surface as well. Meanwhile, if you would like to perform a Genius search for new music, go to the iTunes store and click "Genius Recommendations" in the "Quick Links" section to the right.
Apple clearly wants to promote its Ping feature, but it would be a shame to see this done by removing useful features of the program.