CNet has a good read up about the pitfalls of the new iTunes Plus that Apple has been pushing as the next big thing.
It is interesting to note that while you can buy the songs DRM free Apple has still chosen to tag them with personal information. This means that if a "DRM free" song is loaded up on a P2P site it can still be tracked right back to you.
There are some other pitfalls too, since iTunes does not use the .mp3 format you cannot simply load these songs to any player. The player has to support ACC files with the .m4a extension.
The last big thing is converting your existing DRM laden files over to DRM Free. This is a costly affair as each song will cost about 25% of the original purchase price to convert.
Oh one more thing, when converting, Apple does not let you chose what to convert and what not to. It is all or nothing.
Read more here.
Although iTunes Plus files feature no copy protection, files downloaded still contain the email address you have registered with iTunes. So although files can physically be shared with, and played by, friends and family, any of your purchases that end up on file-sharing networks, for example, can be traced back to you.
If you're interested in an easy way to check your own files, find an iTunes Plus file on your computer. Then choose to open it with a text editor (Windows Notepad works fine). It'll take a while to open and will appear to be full of nonsense text, but if you choose the 'Find' option and type in the email address you have registered with the iTunes Store, you'll find that your DRM-free music is not personal information-free.