If you missed the note and you have iOS4 (new iPhone or new iPod Touch running the iOS4) users please ensure you add the new configuration profile patch to the latest iPhone or iPod Touch prior to connecting to Exchange Server or Exchange Online.
Where do I grab the configuration patch?
Information about obtaining and installing the profile can be found in the Apple support knowledgebase, Article TS3398.
What if I don’t patch the new iPhone or iPod Touch for Exchange?
Failure to install this patch may result in a degraded performance for iOS4 devices, including the inability to connect to Exchange and Exchange Online via ActiveSync to synchronize message and calendar items. There may also be some server impacts so it is worth patching to avoid any issues.
What does the patch do?
Apple tweaked a couple of sync and polling intervals to eliminate these performance issues.