I think I found the solution .
Windows 8 font Rendering depends heavily on the machine it is used on. For example on a brandnew Asus Laptop with Intel HD graphics all is perfect out of the box.
On a 4 year old Toshiba with Ati 4650 ( win8 inbox Drivers ) everything Metro and IE Looks horrible and tweaks are needed :
You Need to Bypass Internet Explorer 10/11's fontsettings how to render text. It seems that almost all Metro Apps use in fact the IE engine or whatever systemfiles that depend on it. Remember that Metro Apps are almost all written in HTML5 and Javascript. So to say they are nothing else but boxed Websites that live on the startscreen.
To do so you must open Internet Options from Controlpanel and go to the section where it allows you to ignore the webmaster's font style on your visited Websites. After you click this first Setting, you click on the second button "Fonts" and Instead you choose here what specific fonts to use for IE/Metro Content text. Try Tahoma or other eye-friendly Fonts and choose for example "Consolas" for fixed Fonts.
Optionally double this Setting with disabling Hardware Acceleration in IE's advanced Settings and you should notice a difference in your next open Metro App and within IE10/11 .
This works exactly the same in Win8 and 8.1.
My Windows is german, so the screenshot Shows you the button to click, but I don't know how the Setting is named in US/EN Versions .
Simply find the circled Control Panel Setting and click first button labeled 1 , choose "ignore font style".
Then button labeled 2 and tell IE which fonts to use.
Hope this helps some People .