Beauty! I like it. Definitely classy, not ghetto!
If you ever feel like refining your design some more (especially if you want to consider selling them), you might consider using a removable motherboard tray. That would take care of the gaping hole for the card slots, and would probably make mounting the ATX backplane easier.
I don't know much about motherboard trays, who makes them, or if they're available separately from the case, but you might as well look into it.