If you have an ultrabook that can dish great resolution, Windows 8.1 does some interesting things around scaling in the UI. This has caused me some grief with my Lenovo Yoga 2 Pro that wants to dish 3200×1800 natively.
Windows 8.1 will try and do some scaling options for you and it feels like a bunch of adjustment areas that you just need to play with for a while to get what you like. You have scaling, screen resolution, magnifier, and other options in the various display settings to mess with. But, even if you do that, some apps can look a little blurry. This is along the lines of the issues Mac users have with their retina screens.
No matter what you do with the various display settings, you should also look at messing with the compatibiltity settings in Windows for the apps directly. If you have a shortcut pinned to your taskbar or on your desktop, you can right-click and go into properties.
Once in the shortcuts properties, you can check a flag to disable the scaling Windows wants to do to to the application rendering under the compatibility tab. Check the disable scaling checkbox.
In my testing, this has helped tremendously on many different occasions. For example, on GoToMeeting it has been critical to kill the blur as Windows tries to offset the high DPI with scaling up or down. You can right-click the GoToMeeting icon when it is running to change the flag. It does require the application to be restarted to take effect.
This is not a silver bullet to fix blurred windows or fonts and it should be tried after you have done what you can inside the various display and fonts scaling areas in Windows Control panels.