Dude, if you were dragging in an mp3 for reference while doing audio engineering work, then you've been doing it wrong for 15 years. Some of us in this space can actually tell you which specific AD/DAs or pre-amps were used in a specific recording or instrument by hearing the final master. I suppose it all boils down to what kind of sound you're working with, but I have *yet* to meet an audio engineer or technician that would prefer to use lossy formats or one that would export a master in mp3 format. For what its worth, I cut records on the side with a decent lathe, and would *never* and will *never* accept mp3 masters from someone if we're talking about music production and replication. There is too much to lose in the process.