Boojum if you believe all that why do you run a 788, 2 722's, DPA omni's, Schoeps, ect. ( i might add that's a mighty sick setup {minus the shemps} lol) Why not run a pair of mics>minidisc? Do you record in mp3 to the 788? Just curious.
A quick answer as to why we should not record directly to a perceptual Codec is because it does not tolerate post processing. For example, the MP3 Codec may discard low frequencies that are below the threshold of hearing relative to the overall program level. However, if you wanted to process the initial recording by boosting the bass, there may not be any bass to boost if you recorded in MP3. Perceptual Codecs may be OK for music distribution, but not for music production.
Chapter 10 of "Principles of Digital Audio" by Ken Pohlmann is a good introduction to perceptual coding. It is not light reading.
The quality of perceptual codecs depends on many factors: psychoacoustics, implementation, bitrate, listening conditions, listener experience and acuity, etc. When everything is done right, it can sound pretty good. The irony is that the main reasons for using perceptual Codecs, namely reducing bandwidth and memory use, are becoming less important.