I think the most shocking thing announced by Microsoft yesterday is that Final Fantasy XIII is no longer going to be PS3 exclusive. Holy shit! Major blow against Sony, IMO.
I probably wouldn't put so much weight into the Mii-ripoff thing. I've heard that you can still keep your old avatar thingy if you'd like. The other game companies are just upset with Nintendo's success and want to be able to say "Yes, but we can do that too!" I doubt it'll have that
much effect on the 360's original appeal, though.
Edit: Not quite related but Nintendo's E3 conference just totally fucking blew. Nothing that we didn't already see coming from many months ago, and nothing particularly interesting at all.