Retiring Exchange 2003

Hello - we've recently migrated our Exchange 2003 mailboxes over to Exchange 2010, which is on a new virtual server, while leaving Exchange 2003 running and acting as the "bridge" server - mail is passing through it from the Internet and being routed to Exchange 2010 users.  We plan to finally shut down this Exchange 2003 server, take that IP address of the old server (which is configured in our MX record and attached to the public IP that mail comes to), and assign it to the Exchange 2010 server so that mail will then route directly to 2010.  Is this fairly straight-foward to do and expect mail to continue flowing as it does now - or is there a gotcha in there somewhere?  Just looking for some experts to weigh in on this.

Thanks