In these days Google has launched its Google Sync service, the response to the most frequent request from the Gmail users: having push capabilities on mobile devices. Now Gmail is able to support push technology.
Unfortunately, there’s a problem with the iPhone: if you don’t have an Exchange account configured, all is OK and Gmail push works great. But what about if you have a previously configured Exchange account, for example with your corporate mail server?
The iPhone can’t sync to more than one Exchange/ActiveSync server at a time!
The iPhone can sync email messages to any number of IMAP or POP accounts without a problem, but it can only sync to a single ActiveSync server at once. So you can set up Gmail over IMAP, Yahoo over SMS/IMAP, your local provider over POP, a Gmail Apps account over IMAP, etc at the same time as your work Exchange server without a problem. But you cannot set up more than one Exchange server using ActiveSync.
If you don’t want to loose your corporate mail server synch, no Gmail push for now… 
The iPhone natively supports the configuration of a Gmail account, so why not working directly on the software in order to support pushing? Apple and Google, please work on this…