As mouse-mazes go...
... this is one of the best I have seen... if not the best. But I am with a few others on this, in that I don't find these things very fun to begin with.
Also, I noticed that you set the quality to Medium from the get-go. It seems kinda sad that something as simple as a mouse-avoider game would cause that much lag. The underlying engine can not be very intense on this... if it is, you have done something wrong. Although the "hitTest()" method with shape flag true is somewhat of a process hog because Flash needs to account for entirely amorphous shapes. It must be the graphics causing much of the problem though, since they are pretty high-quality, and you do get to points where there is a high amount of animation on-screen.
While very good-looking it is not something I will find myself playing again.