My company runs Exchange, and I have MobileMe for personal use, and I'm finding both rather awesome at the moment (though Exchange is a mess on the admin side -- no idea how monstrous MobileMe must be over on Apple's end).
I originally kept wishing for Gmail Push, but Gmail has decided to hate me lately, so now I'm not sure what a useful alternative would be...
BB Connect for iPhone? Er... pro'lly not...
