Holy cow that's bright! I think that would drive me nuts.
The main things I changed were the window borders and the cast bar. I made the window borders use the im list border (with a darker background) rather than the default UI look, and I just toned down the white glow/gloss on the castbar a bit (just darkened the alpha). I'm also using a different unread overlay for chat/ims and a customized version of ArenUI's vitals.