I don't understand the lack of folders complaint. Labels achieve the same thing, and more flexibly, even, since the same message can show up in various places, and its read status is what it should be.

I use evolution for work email and use its "vfolders" extensively. They have a different name, and they predate "tagging", but they're really the same thing, and difficult to live without.

In gmail, I would prefer proper threads instead of "conversations", but in practice the difference is minimal.

The crappy editor is its biggest problem, but even that can be worked around.