Spark up your iTunes and you'll be offered an update to 9.2, go on... it's okay, we'll wait...
The new upgrade features a few essential improvements if you're planning on buying an iPhone 4 or installing iOS 4 on your 3GS. For starters, it allows the software to sync properly with the new handset, including better support for iBooks 1.1, bringing with it the ability to organise and sync pdf documents (to read on an iPad, or an iOS 4-sporting iPhone or iPod touch).
Folder support for apps - one of iOS 4's major new features - is now integrated into iTunes. And there's faster back-ups for iPhone and iPod touch, plus tweaks to how album artwork is displayed which makes that process quicker too.
Obviously, the major improvements will become apparent when iOS 4 is available for public consumption on 21 June, let us know what you think when you've given it a whirl?