If I should be wrong, I may ask, why didn't the kde-team give advice to the distributors to do their job properly.

I think that may be where the real problem is. Maybe the packagers just aren't building optimally (not to complain - their efforts are appreciated). I know that I thought kde2 was slow until I found the thread here on the dot about how to compile kde (and qt in particular) correctly. It has been speedy since then. I used gnome for a week or so, and it wasn't any faster than my kde2 desktop.

Aside from that I can only assume that the speed issue is more subjective than anything, because I just can't relate to your experience. For me, kmail opens quickly (certainly quicker than Outlook did) and I never really feel that I'm waiting for it. Anyway, I hope it gets worked out.