I think the original thinking behind people boycotting ID3 tags was due to incorrectly reported track length information for VBR encoded MP3s.
Earlier versions of Winamp and many other software MP3 players failed to read VBR information from the header of the MP3 correctly, or at all, if there was and ID3 information before it. Some still do (MS WMP for example).
It is discussed in length at r3mix.net. As with most static pages on that site, the information is a little out of date now, but it's relevent in this situation:
http://www.r3mix.net/noid3.htmPersonally (with the new versions of Winamp at least) I've experienced no problems with VBR files, ID3 tags, and track length reporting.
As far as I know, ID3 tags do not, and more importantly
cannot, affect sound quality of MP3s.