TB is one of those programs I've slapped on and never even considered using anything else since. Just works. Reliable. Works well using the forwarders from Hotmail and Gmail. All the features I need.
lol christ, that takes something else
Not personally a fan of the MS kit to be frank, and it's already been established TB works rather spiffingly. I think MS should be concentrating on interoperability rather than pushing anything else. It does however feel a little odd that with all the obvious hard (and very effective) work that's gone into W7, that a mail client would be overlooked. Doesn't mean I'd personally use it, "if it ain't broke, don't fix it" comes to mind there.
*On a slight edit, if anyone's worried about this person being from anywhere other than MS, it would appear he is genuine*