MobileMe has been push on my iPhone since day one. I don;t know what the problem you have been having, but I get mail delivered to my phone seconds after it gets to the web client.
it pushed from day one....the only issue is that from the computer, it dosent push that minute, because its set to Sync Every Hour or Day or Week, unless you manually hit the Sync button
You iPhone, Me.com and mail will get it that minute.
When you change something via iPhone Or Me.com in regards to your Calender or Address book, both units will note the change within a minute BUT your computer will not, depending on if you have it to Sync Once an Hour/Day/Week. But if you hit the Sync button, it will look for changes.
Same goes backwards, if you add something to your Address Book or Calender via computer, depending on your Sync options, it will not be immediate.