I for one still get confused with their icons. I mean, Archive doesn't look at all like archive, Spam looks like a quota warning error, "move to" looks more like "view another folder", and the lack of borders makes my eyes wander outside of the text all the time. And I have to agree about the uselessness of the importance icon. All my mail is marked as important, yes, i know that, how does this help me? It's more useful to know whether you 've replied/acted on an email instead (that could be a nice feature). Not saying the redesign is absolutely bad, after all it's not a radical departure from the previous one, just some things need fixing.
I really like the importance system. My inbox is in 3 sections: Important, Starred, and Everything Else. I look a Everything Else once per day and can typically blow it all away without reading in a couple of clicks.
edit: As for knowing what you've acted on, I always archive an email when replying. There's a Labs feature called 'Send & Archive', which makes this easy.
