Exchange 2010/Outlook 2003 Mail Delay

I am in the process of building a new Exchange 2010 environment on a new domain to migrate off our existing domain and Exchange 2007 environment.  I have 2 sites, both with a CAS/HUB server and a MBX server.  I have a PC with Outlook 2003 with a mailbox on 2010 and my personal mailbox/PC is still on 2007.  With my 2007 system messages between 2007 users are instant, but with 2010 there are delays.  If I send a message from the 2010 PC to my 2007 PC it is instant.  If I send from 2007 to 2010 there is about a 30-40 second delay for the new message to pop up, BUT if I click around Outlook during that time the message comes in sooner.  This also happens for a message sent from my 2010 test account to itself.  Messages sent on 2010 also show to be sitting in the Outbox even after they are received on the other side.  I have rebooted servers, rebuilt mail profiles, checked firewalls, nothing in cached mode, I am out of ideas.  How can I get my 2010 system to run as fast as my 2007 system.