UI controls in Firefox, Opera, etc. are broken, old-fashioned or blurry (Retina)
All the problem (except the 4th one -- Adobe Acrobat) disappeared recently without me doing anything specific. At first all buttons except the colored default button are replaced with new button styles, and then the default buttons are fixed some hours later. Note that an upgrade to Mavericks does NOT solve the issues, nor any restarts or permission repairs do.

I installed updates for iTunes, iBooks, Mail and Xcode just before the problem disappeared. I also installed a Java VM for running Java applets in my browser, though I don't think all these programs are Java-based. This information might give hints on what actually fixes the ugly UI.

P.S. I just noticed some other changes in the overall UI. Maybe Apple is changing the UI in the background, without showing anything in the App Store?