One of the cooler features of the Galaxy Note 2 is its ability run multiple apps in split-screen mode. The feature, known as multi-window, wasn't ready for prime-time at IFA, but was showcased a few days back in an official Samsung preview video.
However, many new Galaxy Note 2 owners in Europe have noticed that the feature isn't available on their handsets. Normally, it can be activated by long-pressing the back key, however on certain devices -- including ours -- this isn't working. According to numerous forum reports, the cause is an older firmware version on these devices. So if your international Note 2 comes with version N7100XXALIE, you'll find multi-window is unavailable. If you're on the newer N7100XXALIH, as many others are, the feature should work as expected. You can check your software version by heading to Settings > About device.
The reason for the omission isn't clear, though it's likely the manufacturer will update those phones stuck on the earlier firmware at some point in the near future. So full-screen multi-tasking should be just a software update away for those affected. In the meantime, we've reached out to Samsung for comment, and will update this post with any info they provide.