Isn't the "reply all" problem a user issue? If people used BCC instead of a bunch of To's, we'd never hear about it. Heck, I would think email clients would prompt if you tried to sent more than a dozen people without BCC.
I agree with everything else and think "managing group messages" has other issues. For example, it's nice that I can duck out of an iMessage group, but can't duck out of a text message group or email chain.
