About the 20% increase: I just realized that I *have* optimized all the buttons and sliders for performance, but not yet the other displays. So there's definitely something to be gained there. Right now I redraw all of them every time because I haven't added code yet to check if they need to be redrawn (it's just a single function that I need to add for each widget, will do that soon).
Edit: 2-color display in output bars added
Edit: Resizing behavior seems to be fixed (problem was that the window size wasn't written to the new parameters, but it was copied back from them - for some reason only in Windows 7, not in XP).
Edit: Full-screen mode works.
Edit: Just removed another 3000 lines of obsolete code

Edit: Mouse-leaves-window issues fixed.
Edit: Did some minor performance optimizations (probably not noticeable).
Edit: Icon colors fixed.
Edit: Removed some (but not yet all - there are 2 left) memory leaks.
Edit: Working on screen update CPU load. Will take some time, have to stop now, hope to be able to post something tonight.