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for me: what is that "a lot more"? I just want to learn something new (btw, labels/tags are not really new, just redesigned imap folders)

Tags have an important difference from folders in that messages can have multiple tags and you don't think of messages as being in a folder.

Personally I find this quite useful and it definitely improved the way I use email.

Opera Mail had tags quite early on, not sure if it was before Gmail though.

Non trivial statistical analysis of email contents and your interactions with your email to effect decent prioritisation?

That would be my top feature in gmail.