There are no drawbacks to ID3 tags given a decoder and player software that "Does not suck."

Filenames are nice for your own person storage space AT THE TIME. They're completely useless for database driven products like the empeg. And they suffer mangling when brought through some other products and/or operating systems (try looking at those files on a Mac running OS9 - or even in OS X (support for longer names) if you're browsing them from a FAT disk or ISO CD).

One of the most backward and pedestrian things I've read in a long time were the ID3 notes on the r3mix site. I almost tossed his entire preset for the ludicrous and completely uninformed things he said about tags.

Bruno