When you press ALT before clicking on the Apple logo, new options popup.
What new options you mean? Using the option key to reveal additional options in the context menu has been there for quite some time now (I now it was in Tiger, perhaps even before that).
When you press the Windows logo key while dragging your "logged in name", sound icon, bluetooth icons, etc, it will move it, and make it magically disappear so no longer will you see them anymore (yes bug).
This also has been there for quite some time now (at least since Tiger) and definitely is not a bug but normal behaviour. The key you are referring to is called the command key and was previously better known as the Apple key (mostly because of the Apple logo on it).
It would be wise to at least verify that something is a Mountain Lion only feature which isn't in Lion. If you did you'd have seen the above in Lion as well.
More ontopic: how does the social networking stuff work, is it off by default, are you able to disable it? I'm hoping it is not like in iOS5 where you do not have to fill in a Twitter account and yet are still bugged about it in every app that supports it. If you are using a Twitter account it makes sense to have those options, but there is no sense in having those options when you are not using Twitter. I don't want to use social networking so I'd also not like to be bugged about it but it is not like I can't live with it if it does still bug me.