If/when I decide to change to Win 7 I guess I'll give Thunderbird a try. I agree totally, MS seem hell bent on changing or removing what isn't broken, while ignoring the obvious.
Web mail in the form of Google mail or Hot mail may be good for keeping track of emails over a range of differently owned machines, if you own a desktop and notebook for instance. I check all my important email from my desktop using Windows Mail and use web mail (I'm not so sure about security with a web mail account) for less important emails and spam trapping.
I've used OE from the beginning and it's always done what I want without fuss, Windows Mail was OE with new clothes but again no fuss. Now with Win 7 I'm going to have to either use something I'm not keen on in the form of web mail or learn another application in the form of Thunderbird or similar.