Incorrect again. According to Microsoft, to "Adjust for best performance" turn off all the candy coated crap...
*sigh* Perhaps you should educate yourself? Aero is an accelerated interface provided by DWM. Turning off DWM (thus all of the 'candy coated crap') reverts the interface to an UNACCELERATED 2D interface. What is faster? 3D acceleration by a GPU or 2D software rendering? Hell, even on the Intel 950, with Aero on is faster than the unaccelerated 'classic' interface.
I don't think you've read up enough about the interface on MSDN... GDI/GDI+ acceleration (e.g. provided by your video card) was removed with Vista (which is why IE under Vista is actually a tad slower to render content). In order for Aero to be present, hardware acceleration must be present (i.e. a video card that has Pixel Shader 2.0, etc.). Thus, faster.
Incorrect again. I've used it on multiple desktop and multiple servers.
Vista is not a server OS, so I take it you've never touched something like a DL380 G5...