If you are reading this, you are probable having the same problem as I am:
After you switched to the iPhone 5, Exchange mail is no longer PUSHing to your device. I have done testing and this problem affects:
1) iPhone 5's running connecting to Exchange 2007 or Exchange 2010 servers.
This does not effect:
1) my iPhone 4S running iOS 6 Beta 6.0 10A5376e
1) Wiped phone and started with completely fresh iOS 6 on my iPhone 5. The only thing I did was add my exchange account.
-Still had same issue.
** How to fix this issue:
1. Go to Mail, Contacts, and Calendar. Click "Fetch New Data". Make sure push is on.
2. Go back to Mail, Contact, and Calendar. Click on your exchange account. Click on "Days to Sync". Even if it is set to what you want this on, chance it to a different setting (i.e. 1 week). You can change this back later, but this is the only way to fix it.
3. Go back to Mail COntact and Calendar. Click on "Show". No matter what this setting is on, change it to a different setting. (i.e. 100 recent messages).
4. Reboot your iPhone 5
5. Exchange PUSH will be working now.