It's as smooth for me a 7's DWM was.
On my desktop with a highend spec it worked fine, but on a decent spec computer, the performance seems to be bad with over 3 windows open.
Also stated by the author of this:
modify vertex buffer to always redraw whole window texture. It surely brings some performance penalty and does not work for windows which are totally obscured (because Draw function is not called for them at all). For other cases, this works perfectly.