This is neat . You have a good selection of samples, and the control over the sounds is pretty impressive.
Manipulating the elements is kind of tricky, though. Especially rotating notes. You start rotating and it rotates away from the mouse and suddenly you don't have control any more. I think bigger "handles" on the objects would be nice, like a circle that pops up around the center when you hover over something and as long as the mouse is in that circle you can control it.
Or perhaps you click on an object to select it and it gives you transform handles to manipulate it. Clicking something else or right-clicking would make the transform widgets disappear.
Also, I'd think it'd be neat to have a bit of a timeline control in the hud. A bar that sweeps across or something. Then you could toggle a spawner or a note on and off, and when the timeline reaches that point it will toggle that item accordingly. I couldn't really make anything except simple loops, and being able to turn elements on or off automatically over time would allow you to create more song-like arrangements. I dunno, just an idea
Oh yeah, and obviously it worked fine for me. I'm on XP. Maybe it's a shader thing?