Hi brynn!
Thanx for the answer!
In "Preferences">"Input Device" there is just one important entry, as far as I see: "Use Pressure-Sensitive Tablet (Requires Restart)". This also exists in the "Input-Device"-Dialog, in the "Edit"-Menu. It's activated in the Standard-Presets in both Dialogs. It's just the same, I think.
I forgot to say, that it is important to start Inkscape with the Pen of the Graphic Pad. Anyway, I also did that and got one entry for my Mouse ("Core Pointer") and three entries for the Pad in the Input-Device-Dialog: The main entry "Wacom Tablet" and the two subentries "Wacom Tablet Pressure Stylus" and "Wacom Tablet Eraser". They are all set to "Deactivated" in the Standard Presets. So you have to set the entries for the Pad to "Screen" (not to "Window"), save it and restart the program after installing Inkscape, to make them work (just the same as in GIMP). I did that many times in the past and sometimes it worked. I also remember that sometimes it did'nt, but I don't remember why and if I could solve the problem. However this time it does not work. Whenever I chose the right presets and restart the program, the presets are set back to "Deactivated" after the restart. I can draw with the Pen, but the Pressure Sensitivity does'nt work. I also tried to deactivate the Core-Pointer, even cuted the Connection, but even that did'nt effect anything. Don't know if it is enlightening in any way, but I tried the Pressure-Sensitivity of the Vector Function in Krita some minutes ago and it did work (but I prefer Inkscape).
This problem only exists in my Windows 7 OS. It works fine with Ubuntu. But I think that I have an older version of Inkscape under Ubuntu. Must check this some time.
Looks like a bug or some kind of malfunction in my Windows-System. Don't know any other presets to fix it in Inkscape or otherwise. Any Idea?