>Plus you can even switch to emergency back up AA's if you >need to.
Well, the AA option sure was a nice concept, but as far as I'm concerned it's a non-option. I put a set of six brand-new alkaline AA's in my MB-D100 and got about six shots before they couldn't handle the load. The camera kept giving me "err" and the mirror would lock up.
I am not the only person to have this bad experience with AA's. There has been at least one thread here about them.
I can't remember if anybody has tried Lithium AA's with better results.