Everything went well, which isn't always the case when I upgrade my iPhone OS . All my settings and synced items transferred over after the upgrade to iOS 4 finished, and all my apps worked.
The actual iPhone upgrade takes about 5 minutes but the restore of your stuff can take quite some time depending on how many apps, tunes and videos you keep on your iPhone or iPod Touch.
Note that iBooks isn't automatically installed and you'll have to download that free app separately in iTunes. Watch our iOS 4 on the the iPhone video to see iBooks in action on the iPhone. We also demo how you create folders and manage multitasking apps (assuming you've installed a few updated 3rd party apps that support multitasking, otherwise just the Apple built-in apps support multitasking).