Without an iPad to connect, there aren't a whole lot of visible changes for users to notice. The Audiobook library category has been renamed "Books" and broadened to include all book-related content, including audiobooks and back-ups of e-books purchased using the iPad's iBooks app. Although the feature isn't advertised, we found that free EPUB books from Project Guttenberg or Google Books can be imported via drag and drop. Unfortunately, without the option to view e-book files within iTunes, the new feature is useless without a compatible device with which to sync.
Version 9.1 also blesses users with the option of deleting, renaming, and rearranging Genius Mixes. Perhaps this is an admission on Apple's part that the company cannot, in fact, read your mind. At least, not yet.
Along with a slight redesign of device view, the device sync summary page now offers a checkbox option for converting "higher bit rate songs to 128kbps AAC". The option for down-sampling music files on-the-fly was previously available only to iPod Shuffle users, who presumably cared less about audio quality than about cramming as much workout-worthy techno on their devices as possible. After hearing a handful of user reports, it seems that all iTunes-compatible devices now include this down-sampling capability.
Other pieces of general housekeeping include the shortening of the Applications category to "Apps" and a few tweaks to overall performance.
Users with jailbroken devices (iPhone or iPod Touch) are reporting an inability to sync after the software update.