Everything I buy from iTunes is something which is simply not in print on CD or something which is ridiculously overpriced on CD.
I prefer to own stuff on CD for now, until iTunes comes up with a truly lossless format.
My CDs remain higher-fi than iTunes for now.
A recent article in Mojo magazine said that with online services like iTunes (which are now seeing the rerelease of titles that have been out of print on CD and vinyl for over a decade), titles may never go "OOP" again.
And with some out of print CDs getting $40-100 used on Amazon, it is in the artist's best interest to license them for download (unless the artist is sitting on a hefty stack of unsold CDs).