Hmm, some interesting iTunes observations have been posted on Digital Music News. They relate to the recent announcement by Apple chief Steve Jobs that DRM-free tracks bought via iTunes Plus, originally more expensive, would fall in line with standard DRMed tracks - 99 cents in the US.
DMN points out that when iTunes Plus was first launched existing customers were given the option to upgrade tracks they had already bought with DRM, which were now in the Plus catalogue, to DRM-free by paying the price difference - thirty cents. That option apparently still remains, even though the DRM-free tracks can now be bought for 99 cents, meaning you might argue the upgrade should now be free.
Which is a bit odd, though possibly caused by Apple's licensing agreement with EMI more than anything else. In reality most people wanting to upgrade previously bought DRMed tracks already will have done so, but the situation is another example of Apple price cuts penalising their early-adopter customers - you'll remember there was outrage when Apple made significant cuts on the iPhone price point just months after its launch in the US, so much so they offered those who had bought the device at the higher price Apple vouchers to compensate.