Any Manual Focusers? Chime in here

on how the hell you know when you got focus, because at least on the lower Canon bodies - XT, XSi, 40D, even. I can tell via the view finder - actually, it looks in focus and then I take the picture and it is not, i.e. just because it looks focused in the viewfinder does not mean it is in focus, i.e. the viewfinder is useless for focusing.

Phew I thought it was just me (I have a 450D)! Through the viewfinder it looks spot on, afterwards I find out I have the usual microphone is in focus issue. I thought I was just being rubbish. I have less problem with my 85mm f/1.8 than the 50mm.
Although doesn't everyone use MF? When I asked some gig photographers before my first ever gig I was told to always focus manually.

Have you guys tried adjusting your diopter?

I find AF to be plenty accurate, more accurate than I can get with MF of moving performers.

With AF, in good light I find that it's generally an issue of whether I got the closest eye, the far eye or the mic perfectly in focus...I'm not quite that accurate with MF. However, in extremely low light I will resort to MF with live view.

High precision focusing screens should help with MF through the viewfinder, but unfortunately they are not quite as bright as the standard screen.