Surface Pro 3: 12" @ 2160x1440 => 216 PPI
MacBook Air 11": 11.6" @ 1366x768 => 135 PPI
MacBook Air 13": 13.3" @ 1440x900 => 128 PPI
MacBook Pro 13" (Retina): 13.3" @ 2560x1600 => 227 PPI
(Rumor) MacBook Air 12" (Retina): 12" @ 2304x1440 => 226 PPI
Poor, blurry Google Chrome.
Edit: I was inspired to look into it a little more, and it looks like Chrome does have high-DPI support: https://groups.google.com/a/chromium.org/forum/#!topic/chrom...
It has to be enabled by a registry key and seems to break Chrome's notification tray icon.
XMind, for example, has icons that you can hardly see on my Pro2.
Unity3D's GUI scales up correctly but there are a whole load of fixed-sized panels that become too large to be useful.
Chrome's font rendering is still screwed even on low DPI windows machines, especially if Google Web Fonts are used.
Asus Zenbook Prime: 13.3" @ 1920x1080 = 166 PPI
Lenovo Thinkpad Yoga: 12.5" @ 1920x1080 = 176 PPI
Lenovo Yoga 2 Pro: 13.3" @ 3200x1800 = 276 PPI