GUI and Syncing are HUGE.
In particular the syncing. Support for Quicken, Quickbooks & Microsoft Money is very important to me.
I purchased my 7520 for the specific purpose of secure, robust email as well as being able to track my expenses (at some point). I was very disappointed when I found out that the expense tracking applications for blackberry don't have sync capabilities.
So my thoughts are this:
Remember that many blackberry users are responsible for more than just themselves at home and at work. This means that Quick Books must be included in the equation with the other two programs that dominate the market
Extraordinary must be ordinary