I think I already know the answer to this question but I'll ask anyways.
I currently have a Storm (waiting on the DX to ship). On the Storm I can do themes which totally modify the UI (currently using a "minimalist" theme called "Phosphoresence"). From what I am reading I won't be able to theme the DX without rooting the phone, which I don't want to do.
I'm OK with this (I hope so 'cause the DX is shipping soon) as I have 7 home screens to customize but extreme customization would be nice.