Not a thing. True, in the past, iPod touch owners had to pay a fee that was either nominal or infuriating, depending on your point of view. (The iPhone 3 update, for example, set iPod touch owners back $10.) The reason for the charge involved accounting rules: Apple recognized iPhone revenue on a subscription basis, counting the money it got over a two-year period. The nitty-gritty details are probably interesting only to accountants (and even then, not very much), but the end result was iPhone users could download major OS upgrades for free, but iPod touch users had to pay. However, last fall, the on how companies could report revenue on subscription-based devices. Apple quickly (and happily) adopted those new rules for its 2010 fiscal year. So this time around, iPod touch owners don't have to break out their wallets for an iOS update.

You could, but you'll need to manage your expectations. The iPhone 3G will run iOS 4, but some key features won't work because the hardware simply won't support them. We've seen some reports of iPhone 3G beta testers saying the 4.0 update made their phones run slower, though we haven't noticed any performance hits to 3G phones. You might not want to update until you have a truly compelling need.

The most significant feature missing-in-action for iPhone 3G owners is multitasking--you'll still have to quit out of one app to run another as you did with iPhone OS 3. You also won't be able to change your Home screen's wallpaper the way iPhone 3GS and iPhone 4 owners can. And you'll have to make do without Bluetooth keyboard support.