I'm happy to say that we at TACF have our one iPhone updated with version 2.0, and have got it syncing with Exchange 2003. Apple provide a document that offers a trivial level of assistance in setting things up. If you're already using ActiveSync for other devices, then you'll be working already. If you're not using ActiveSync (or aren't sure if you are), but you are using Outlook Web Access already, then you're just a couple of steps away. There are a few guides out there for enabling ActiveSync, which is really a simple matter of enabling in Exchange System Manager, and ensuring it's enabled for the user that needs it (enabled by default for all users).
In our case, we had a small spanner thrown into the mix, because we use forms authentication on Outlook Web Access. I suppose this would affect anyone setting up Exchange ActiveSync, if they also used HTTPS and Form Authentication for their OWA. You can test ActiveSync/OMA (Outlook Mobile Access) by browsing to "http://servername/oma". If it's working, you should receive a login prompt, and then posssibly a warning about an unsupported device, followed by being able to get into some sort of email account display.
We received the following, from OMA:
Outlook(R) Mobile Access is supported only on Microsoft(R) Exchange Server 2003. Currently your mailbox is stored on an older version of Exchange server. Please contact your system administrator for additional assistance.
This is the error manifested by using Forms Authentication with HTTPS, specifically on the "servername/exchange" directory. Microsoft describes the fix in this article. We went with resolution method 2, that requires you to copy the Exchange virtual directory (in IIS), and then adjust registry settings to point to the new copied folder (which doesn't use forms auth or ssl).
After a few IIS restarts and a couple of tests, we had our iPhone syncing like a champ!