Good
Ah, it's done :)
What you have here is good But there is no real clear structure to this song. It's all just ride, and never really gets to where it's heading.
There is a small part at the end which shows a bit of variation, but you need to have some kind of hook or "chorus" instead of a repeated riff sorta thing.
Keep in mind that a bit of dynamics (stops and starts, soft and loud parts) can make any good song a great song.
I am also curious as to how this would sound with vox?