Downside to MP3
When a client comes to me with a burned CDR of music to play when I'm doing sound, I don't judge them. I have lots of my music collection in compressed formats (MP3 or Ogg Vorbis) on my computer, and I've lost some original CDs and had to burn new copies on CDR. When I get a CD player for my car that can play CDRs I may even stop using my original CDs so that I don't lose any more.
However, if you're going to hand me a CDR to play at a public function, on an expensive, high quality sound system that I've spent all day setting up and making sound as good as I can, please, PLEASE don't burn that CDR from highly compressed MP3 files!
Last night I did sound for a wedding reception (which was very beautiful). The one thing that marred the evening for me was when the groom handed me a CDR with the song Someone (Bryan Adams and Barbara Streisand) on it for the first dance of the newlyweds. It had obviously been burnt from a 64 or 92 kbps MP3, and it sounded like TRASH. It sounded all swishy and flangy, like over-compressed MP3s do -- it pained me to have to play that for their special moment. Times like that make me wish I had an extensive library of music on the shop's laptop, so that I could have replaced the cruddy version with something that sounded crisp and clean, like I'm sure the original production of that tune was.