From the rumors we've heard so far the Galaxy Note 10.1 has suffered quite a few changes. That may be because Samsung, like many others, are finally starting to realize that they need to release something that is a little more compelling than the original Galaxy Tab 10.1, and the Galaxy Tab 2 10.1, which is basically the same, but with Android 4.
The Galaxy Note 10.1 is going to be a tablet addressed to people who love drawing mostly, thanks to its pressure-sensitive S-Pen, which is also getting overhauled for the release so it better fits inside the tablet. The original one was much thicker, so now they decided to do it the same as they did it for the Galaxy Note phone.
So far we know that the tablet also got its processor changed to a quad core Exynos chip (probably the same one as in Galaxy S3), and the latest rumors say it will even get the Midgard-based (new GPU architecture with unified shaders) Mali T604 GPU, which will be the most powerful GPU released this year by far (even though the GS3 MAli400 GPU is already the best in smartphones).
One other change I'm hoping for is a higher resolution of at least 1920×1200. The Mali T604 supports resolutions up to 2560×1600, and I'm sure we're going to see that in a Samsung tablet too in the next few months, but at least this one would be better than the same old 1280×800, and it would make this tablet that much better of a sell. It might even make drawing more accurate thanks to this many pixels.