Hm...
Window... although the effect is amazing, as most people have said, is quite angley and circumstantial. You need specific situations which limit your angles and your method.
Interlace, which is equally amazing is less angle sensitive and less circumstantial. BUT, there is a one time set up which will take a lot of time and effort. There is also a little... requirement, which I can't really say but you might just be kinda "aw.. thats a shame". Its not that bad, but you get a little dissappointed.
If you are looking for a Window-like effect, check out Jean Pierre Vallerino's Signed Card Through Window. Exactly the same effect as window but it can be signed. It requires a bit more clean up but still its not much.
I love how in both Window and Signed Card Through Window, the trailers show random ass windows everywhere.