Hmm... guess I'll be odd man out. If I'm doing an all-over design, I like to start in the upper right hand corner and work across to the left about 14" and then back and forth down to bottom at that width. I feel more secure cramming that right hand edge under the throat area if it's already been quilted. So far I haven't had any trouble with it getting out of square, or bunching towards the center as I move left over the piece. I hand baste about 3" apart from bottom to top though, so it's not likely to shift much.
Like you tim, if I do one with a pattern in the blocks, I do ITD and then feel safe starting anywhere I want. :)