I came across this..
maybe it'll help some of you...
http://kmcital.wordpress.com/2008/07/15/iphone-20-mobileme-and-push-gmail-working/
In response to the frustration out there, I have happened upon a working configuration. Yes, thats right!! I have push gmail on my iPhone. Im not sure actually why I was so frustrated not to get my email in a split second vs. 15 min or so later
but push email is just cool. And after all, why should blackberry users be the only ones on email crack!?
So heres what I did:
Sign up for MobileMe yes, thats right, itll cost you. (Of course yahoo push email is free, but Im a gmail lover)
Follow usual setup instructions for MobileMe on your computer and iPhone
In gmail settings, forward all incoming mail to your new MobileMe email address, also choose to Archive messages after forwarding (up to you, really).
Make sure you also have your gmail account setup on your iPhone
On iPhone, change the smtp server in the Account settings for MobileMe, to be the smtp.gmail.com that is used by the gmail account. This is the important step: all outgoing email will have the reply-to info replaced by gmails smtp server to be your gmail address, not your mobileme address even though it came from there.
Go ahead, test it. Send an email to your gmail account and watch it push instantly to your iPhone! Beautiful, isnt it.
Heres another good thing: I was worred that all of my labels in Gmail would not be able to be used now if Im reading everything and replying using my MobileMe inbox. Well, you cant do this on your iPhone, but on your desktop, assuming you also have both gmail and mobileme accounts setup in your mail client via IMAP, then you can drag a message from your mobileme inbox to a gmail folder (label) and gmail knows how to handle it. In other words, no duplicates. The message is in the Archive (All Mail) and labeled with the new folder/label you dropped it into on the mail client. Nifty, huh?
Well, I just got this setup, so Ill see how it works for a few days. You may want to try it out too!