I have looked at iOS 4.2 wrap-ups and all I can see are features for iPad.
Besides AirPrint (which does not work with my printer), is there anything for the iPhone 3GS there?
Among other things:
UPDATE: There’s a trick to use the Find my iPhone in a 3GS or similar. I found out that if you create everything from an iPhone 4 (and/or presumably an iPod TOuch latest gen), you can later go to your 3Gs and enter the same data and it will work. :)