For me Aero Transparency in themes other than the default aren't working in 4.0.280 Stable for Windows, they show up as blue.
Although I am using an RC version of Windows 7, so I'd like it if somebody who's using a full version of Vista or Windows 7 could test to see if they work for you.
Here's a good theme to test it with: https://chrome.google.com/extensions/de ... cofgnnoohi