One more thing: I really would like to get to know more about compatibility with programs besides Photoshop. So far I couldn't get information about the compatibility with GIMP. I wouldn't like to buy Photoshop just for this.
So if anyone hears something about these compatibility issues, I would be interested.
According to their page and the video they show of the export, if you want the file to preserve layers, you do need Adobe Photoshop or Illustrator, or Autodesk Sketchbook Pro 2011+ or Designer. They have their own app that does the initial read from the device, and then you export from that app directly into one of the supported programs (not directly to a .PSD file).
If you don't care about layers, then you can save it as a number of flat formats (JPG, BMP, TIFF, PNG, SVG & PDF) and then use whatever app you like to edit those.
Without being able to include the layers, though, it may not be much more than a glorified scanner.
Especially if the pen itself isn't all that great for sketching with!