Some of you seem to be confused...

Android will run any Android App if you can get the apk for it. It's an operating system like any other.. there is software written for it and it runs.

However, Google's apps are closed source and cannot be distributed. This includes the Android Market, Maps, Youtube, Voice, Maybe even Gmail and Mail etc. These will not be possible to use because the N900 is not an official build with a license with google to have those apps.

Meaning that you are limited to the apps you can get either via direct web download, or third party markets such as SlideMe.

Technically, Android itself is "fully functional".. but it's not going to be the same device as you would buy that was meant to run Android.