NuevaSync -- Gmail push, but for a small price...
I'm not sure if this has been discussed prior... I'm currently trying NuevaSync (NuevaSync - Over the Air Mobile Sync) which acts as an intermediary between good ole' gmail and the iphone for syncing Calendars, Contacts AND GMAIL PUSH.
The service essentially acts sorta like the BIS service of a Blackberry. It's an Exchange Server, which connects to the imap gmail service. thus, you get (and i'm currently getting) push email from gMail.
The price is $25/yr -- 1/4 the price if mobile me, which i was using for a hacked push service for my gmail.
The cons: you CAN already sync directly with calendars and contacts, BUT you cannot have two exchange accounts at once (is that correct? i didn't try).
Let me know what you guys think of the service. Unfortunately there is no free trial. i'll update this post in a week to let you know how the service has been.