BlackBerry Forums Support Community - Going from BES 4.1.7 to BES Express

We are a small shop... 10 users with plans to go to about 15 users in the near-term. Currently we have BES 4.1.7 (on an older server) with Exchange 2003. I like the idea of moving to Express because:

It is a free upgrade; and free is good
No need for CALs for the new users; did I say that free is good?
If I move BES off the older server, I can start my plans to retire it
It is probably a good idea to upgrade anyway

Since we are such a small shop, I'm thinking about installing the BES Express directly on our Exchange 2003 server.

In preparation, I've started to read the installation and configuration guide and I have also read a few threads here.

Is there anything else that anyone would recommend that I do (or don't do)?
Has anyone here gone through a similar experience?
Any other advice?

Thanks!