It's a joke they still haven't fixed the fullscreen feature rendering your second monitor useless. I can't understand why they did it that way and why it hasn't been fixed already.
Agreed, it's ridiculous. I went out and bought SizeUp which, among a ton of other window positioning shortcuts, gives me a shortcut to resize an app to fullscreen on a single monitor, without making the second monitor useless.
Are you sure about that? Apple lists exactly that as one of the features of Mountain Lion:
Go full screen on any display
If you have a secondary display connected to your Mac, you can take an app full screen on either display. Drag the window to the desired display and click the full-screen button.
Everyone keeps saying this, but I think it's FUD. They've fixed the main gripe with Lion's full screen: not being able to full screen an app on the monitor of your choice (as opposed to the main monitor only).
Why is the second monitor useless? I'm sure you can still drag app windows to it and interact with them.
edit: You can drag child windows of the full-screened app to the second monitor. The whole point of the full-screen mode is to isolate the app and give it exclusive focus. For everything else, there's the zoom button.
Well that's the real problem, you can't ... when you fullscreen an app the second monitor just displays a gray fabric background but you can't put apps, widgets, or anything else for that mater on it. It's a fail I wasn't expecting from Apple.
