Tags are superset of folders
I don't understand this comment. As far as I can see tags work just like folders to start with, but allow an email to sit in multiple tags IF you want to. You can use tags like folders.
Gmail has nested tags right now as well. I don't use them so I haven't tested their ease of use. Nesting tags would just be another requirement TBird could subsume.
I find folders impractical because of the volume of my email and I get bored filing. I'd like to be able to intelligently move email to tags / folders. With the number of tags I'd like to use folders would be unusable. I'd need to be able to select tags from the list to combine in a fluid view on all email selected by those tags.
