I loved the dataliberation.org page. Thanks Matt.

I don't mind GMail GUI but I am actually am an Outlook fan (and in general I much prefer a client operating locally). I've several rules that I carry with me from years ago, updating them as needed. In specific folders, I also use labels and I have tens of categories that now make very much sense to me.
Searching is quick and easy.
I manage my PST files and my OST files quite easily, keeping a local copy of all my relevant messages since years ago, which I like and would never give up for an on-line service (which is why I really liked the Google approach to "data liberation" that Matt linked).
Calendar works flawlessly, and I use many of them for a nuber of reasons. I mostly manage two mailboxes with it, one for work on an Exchange server, another one for personal mail on a Kerio server installed locally in my home server.

My WP7 also plays a role in my email overal happyness, I have to say, as I really like its email features a lot.

I have to say I'm quite happy with my email overall setup, at present, which happens to be almost entirely within the MS ecosystem.