Aero Glass/Transparent window borders in Windows 8?

Not really. Windows no longer adds transparency to their windows. Therefore, officially there is no way to do it. You could try this guide:

http://www.intowindows.com/enable-aero-glass-in-windows-8/

However, I am not sure if that works in the latest build. There also might be some third party apps, I'll try to find one after I'm done writing. Good luck.

EDIT:

Alright, you can look at this third party app as well. I can not vouch for it's security though. I have never tried it. Here is an article showing it off.

http://www.addictivetips.com/windows-tips/aero8tuner-get-a-hint-of-the-old-aero-glass-effect-back-in-windows-8/

Aero Glass can be enabled with a DLL available for free here:

This DLL is loaded via AppInit into the DWM.exe and Explorer.exe and and hooks the functions SetWindowCompositionAttribute and DwmEnableBlurBehindWindow and implements them again to enable the Glass effect again in Windows 8.

Now you can work with Windows 8 without getting headache because of the ugly Theme :)