Quick question: is it impossible to close out of programs? I mean, you're just going back to the Start menu instead of actually closing the program, it's still running in the background, eating RAM...
Metro apps are closed on the fly, the moment you run out of resources. A bit like on iOS. As a result you don't need to worry if it's using up ram.
There isn't any advantage in having empty ram, as otherwise it would be in use. Windows 7 will even fill up your empty ram with applications you might
want to use, based on previous usage. As a result you should find an application starts up faster, after you've been using it for a few days.
Although it does feel a little strange, having one set of applications you do need to shut, and another that you don't.