If you're going to use the center AF point only...

MisterBG wrote:

I currently only use the centre AF point on my 30D (unless I'm using a tripod), so switching to the 6D poses no problem as far as I'm concerned.

For a subject off centre, I simply focus and recompose - how difficult can it be?

As regards the "Rule of thirds" - as Captain Barbossa says in Pirates of the Caribbean "Them's not rules, more like guidelines."

--
>The only way of discovering the limits of the possible is to venture a little way past them into the impossible.