Well, I use mine for basically all my listening now, including my MP3s. You can really hear how crappy they are, but whatever. For CDs, I've been listening to...
Steely Dan
Ben Folds Five
John Scofield Band
ulu
Keith Jarret
And some other stuff.
As long as you're not listening to MP3s or a really garbage recordings, they should sound fine. That said, if there is anything "wrong" with the recording, you're going to hear it. Still, I find them quite good. I wear them when I'm studying or working because it really helps to get away and sink into the music. They don't make anything any different than it is. If you're not using a good source (e.g. laptop), you can hear it. If your music was recorded on an analog tape, you can hear it. In all seriousness, I've heard things (mainly in my Steely Dan CDs) that I've never heard before. "Whoa! I never noticed that piano fill there!"
I haven't hooked mine up to a good reciever, but from the sources I've used so far (Portable CD player, Dell Laptop, Korg Triton, Alesis QS 8), they have all the freqency range and SPL abilities you could wish for, and of course great sound quality.
The best part about them is that they can be your "go everywhere" headphones. Plug 'em into whatever and you'll be assured top-quality sound, in the studio or just on the street with your portable.
I'm rambling, but I think I answered your question. Ask something else if I didn't. I'm quite tired and incoherent at the moment.