iTunes 9.2 is available for download, ahead of the release of the new iPhone so features specific to that device will be functional when it arrives. Beyond this, the update addresses problems with album artwork displaying slowly, and includes a few new features such as syncing PDF documents as books, and organizing iOS4 apps into folders. Since iTunes 9.2 will be required for use with the new iPhone, if you are planning on upgrading your phone you might consider getting the software installed and ensure everything works on that end before upgrading your hardware.
The update is available for OS X 10.4.11 or later and 10.5 or later, as well as Windows (32-bit and 64-bit). For the Mac, the file will be around 100MB to 120MB in size, and should not require a restart. You can get it from Software Update, as well as a download from the iTunes website.
Specific enhancements in this new version are:
Sync with iPhone 4 to enjoy your favorite music, movies, TV shows, books and more on-the-go
Sync and read books with iPhone or iPod touch with iOS 4 and iBooks 1.1
Organize and sync PDF documents as books. Read PDFs with iBooks 1.1 on iPad and any iPhone or iPod touch with iOS 4
Organize your apps on your iOS 4 home screens into folders using iTunes
Faster back-ups while syncing an iPhone or iPod touch with iOS 4
Album artwork improvements make artwork appear more quickly when exploring your library
As always, be sure to have a full backup of your system (particularly your music, movies, apps, and other items handled through iTunes) before updating, and be sure to have a backup of your iTunes library as well. The new version should preserve your old library and update a copy for you; however, making a manual backup ensures the backup is done correctly.