I didn't buy one of the new 4th generation iPod touch models (nor do I plan to). However, my 1st generation iPod touch had an iPhone OS 3.1.1 update available for it when I plugged it in to iTunes. As you might guess, the update for the iPod touch is a subset of the one for the iPhone. Some of the interesting updates it shares with the 3.1 update for the iPhone are:

- Remotely lock iPod touch with a passcode via MobileMe
- Anti-phishing feature for Safari
- Improved Exchange calendar syncing and invitation handling

The update for the iPhone itself includes the following new iPhone-specific features:

- Save video from Mail & MMS into Camera Roll
- Save as new clip after trimming a video (3GS)
- Better iPhone 3G (specfically) WiFi performance when Bluetooth is turned
- Voice control on 3GS with Bluetooth headsets
- Paste phone numbers into keypad