Today Apple and the music industry's third largest label, EMI, unveiled that EMI's catalog will be available on iTunes without any DRM (Digital Rights Management). Removing DRM means you can get songs of higher audio quality (CD-equivalent) and without the restrictions on number and type of devices you can put that music on. Basically, you can do what you used to do with your CDs - play it anywhere, anytime. You're no longer tied to an iPod only, and no more limits on the number of computers you can transfer to.
The cost of all this freedom? An extra $0.30 per track. And you can convert anything you've already purchased through the iTunes store already.
Why is this such a slow process? The music industry is afraid that removing DRM means that people will send music to each other and not buy their own copies. But the more likely scenario is that more people will be buying music online because they're not locked in to specific software and/or hardware by doing so. Multiple studies have shown that people are more willing to buy music without DRM than with. Hopefully this model proves successful and the other labels follow suit (and maybe the price comes down). You should be free to do what you want with your music after you purchase it.