Speed & Stability
If I could give it a 6, I would. Edge's windowing system is that fast.
The reason I chose to review Edge .60 and not .61, is that the .61 demo only has one window showing, this demo has 2 which really show off how fast the windowing engine is.
Edge doesn't have much, just a launcher and some windows. But they work very well and very responsively. Plus the code is included, so you can try to get ideas for your own windowing system, or maybe use Edge as your base?