Mass Effect 2 Difficulty System Suggestions Wanted

Mass Effect 2 lead system designer Christina Norman stopped by BioWare's official forums to ask for feedback from the community on how the game's difficulty system should be set up.
We already have a really great plan in place for our difficulties on ME2 but I'd like to hear your input, and it's not too late to make changes if some really good idea come up.

What would you like to see out of Casual, Veteran, Hard Core and Insanity difficulties on ME2? How would you like to see them differ from Normal difficulty?
Since you can't play the same character through twice, does it really matter? I don't see myself playing harder difficulties for anything other than the achievements anyway.