I'm running 8.1 on a 13" 1080p laptop (2010 Sony Vaio Z). First party apps seem to be DPI-aware and scale fine. Some third party apps are not DPI-aware and use the new pixel doubling approach. The most surprising offender is Chrome, which is so critical since fonts look grainy and blurry when pixel-doubled. Fortunately each individual app can be overridden: properties on the start menu shortcut / Compatibility / Disable display scaling on high DPI settings. After setting that, Chrome renders at 100% again, so some UI elements are too small--but at least its internal zoom mechanism works correctly for fonts on web pages.