So far, I just found the position bug in Windows. x is not considered, I created a ticket in ur repo.
Another strange thing that happened to me (Macbook 15" retina, using VM with Windows) is the actual pixel size of the WebView, seems 1/2 the size of the stage, so it doesn't take into account the AIR scaling factor or the current OS display resolution. Not a big deal, but I guess it could be consistent with OSX.
The performance on the Starling side with all the testings I did, is steady at 60FPS.
WebGL on Windows, as u said, is not supported by default, unless Settings::cef.bestPerformance=false. Making a simple test though, it renders this 3d scene super choppy (slow), but it shows constant 60FPS on the HTML monitor and doesn't seem to affect the Starling's performance either, idk why.
All the target="_blank" links that u click, opens a new window, which seems weird, but i don't mind...
Overall, for most HTML5 usage, the rendering and performance is really good on both platforms, you can definitely tell the difference with StageWebView 🙂
Thanks so much for the ANE, and keep the good work!