Dave yes you are right. when it comes to certain circumstances, a representation that is sonically very close is good enough, like an ipod for example. Have you ever seen the differences between an mp3 and it's original wav file with a good editor though? what a difference! The harmonic shelf is literally chopped like an axe hit it. It is totally missing, and editing by frequency instead of time is nearly impossible because their is really no telling where the thing is going to go harmonically. I have noticed that if you enhance high frequencies before compression, it helps somewhat, but if you add more than a max of 6 dB to a 50% signal to anything about 8K or above all you wind up with is a bunch of end order siblance. Do that and you may as well record the sound of a metal rake against a cement sidewalk. I can't really knock down Fraunhoffer mp3 type compression so much though because it is a heck of a lot better than anything else that anyone else to date has come up with.
In short, mp3 of higher bit rate are acceptable for casual listening, but dont think you are going to be successful at any kind of frequency editing methods when it is put up on the editing block. Once you magnify it and look for splitting zones, you will say, What is this?, because it does not even 'look' like music at that level! Thanks! At least we are all on the same page and understand just what an mp3 is: a DIGITAL REPRESENTATION of sound that is incorrect in harmonic structure, if having any structure at all.