Hi Stefan, yes, yes, good points from a man who knows what he wants in his email client :)
I think Mail.app will continue to evolve in the directions you mentioned. But I do like the current version more that you do. I think some of it is personal taste. For instance, I like being able to choose from my set of signatures regardless of which account I'm using.
You didn't mention the new junk mail filter, which is outstanding, especially during the current spam invasion we're enduring. And unlike Entourage, I haven't heard of a case where Mail.app mysteriously crashed and vaporized all the mail. Beware of the Entourage database.
As for speed, it was one of my three "must have" requests from Apple in my open letter.
Thanks for your comments!