Multimon seems to have been thought only for side-by-side monitors configurations, mine is vertical with one monitor on top of the other. Not working for me...
+ other issues...
1- App Store only, no demo ---> I lost $10
2- Does not allow windows to be expanded across 2 monitors. If I do, the window snaps to one monitor or the other after a second or so. This is a deal breaker for me.
3- Menu mentions "left monitor" and "Right monitor", no option to change to Top and Bottom like I have.
4- Clock display does not follow my System preference for 24-hour format. Tutorial says setting available in Preferences, but nowhere to be found.
5- The green dot on each window looses its "toggle" functionality, i.e., in Mac OS X, one click maximizes window and the next click brings it back to original size/position, but with Multimon. only maximizes. I don't want to loose the Toggle functionality!
6- Multimon menu is supposed to appear at the end of each menu bar, but only appears in one menu bar.
On the good side, this is implemented as an app, so it is easy to start and stop, not some system-level add-on that require rebooting.
This app does not work for me, it may work for some people though.
About my ratings, Macupdate forces to rate "Stability" but I don't have a real opinion, just it didn't crash for the short time I tested the app.