Really. Stop. The old iPods have different hardware that makes them unable to handle the new features. If you noticed, the minis (released a year ago) just recently got the new features to make them pretty much equal to the 4G. Would I like the new features on my 3G? Sure, of course I would. Are they showstoppers? Is adjusting the playback speed of an audiobook really a showstopper? I really do not think so.
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The answer is this: eBay has been seeing inflated selling prices for iPods for well over a year now. Sell your old iPod and buy a new one if you really want the new features. meanwhile, for those of us who have to support multiple different iPod models in their household, this is useful.