Oh, sorry! What the 2.1+3.0 combination gives me is the ability to run newer Sense stuff on older Sense 1.0 phone hardware. I don't think the Evo 4G could handle everything being Sense 3.0. Actually, it could probably handle it but it wouldn't be as smooth.

This isn't anything I did though -- this is all how the 3rd party developers cooked the particular ROM I'm using. It's not as if I made a conscious, wise decision to combine the two myself.