I like the ... 5/4 (?) signature you've used. I usually don't divide my 5/4 beats like you do. It's wonderful in how many ways you can divide that signature.
The sudden changes were welcome too! Makes it really sound like something is going wrong.
I wonder if this is actually possible on a real SID-chip, it has quite a lot of depth in terms of stuff going on at the same time. But if you tried to imitate the SID-chip, I assume you know about it's limitations. So if you did keep the limitations in mind, it's pretty mind-blowing what you did. Creating a whole world of sound with just those 3 tracks.
I'll have to show this to Jeroen Tel sometime.