slow as hell.
I had the same prob.
in etc/x11 you have the file XF86Config-4
add Option "RenderAccel"
That helped mine a bit
And of course the lower ur resolution is and things it has to load such as: the files it loads in kde or gnome the u have all the things in services to...
Even check if ur dma is enabled on ur hd.. do this with hdparm.
I tweaked my system as i wanted and it toke the slow loading away. but dont ask me exactly what it was.
Hope this could give u some idea. maybee ??