Important notices from my short experience with exCanvas:
First: it's of course slower than native implementations.
Second: using drawImage with 32bits PNGs reveals the beauty of IE7 claimed support of PNG32 ... it fails miserably : the transparent areas are opaque.
I have not tried various globalCompositeOperations but a quick googling session did not bring anything about VML and blending modes, therefore I doubt exCanvas support anything but the default globalCompositeOperation
In short, it's a nice thing to have but it's far from covering the use cases of Canvas.
