This is pretty good!
The way you eased from the synths and drums into the more intense guitar parts helped to nail the ominous feeling you were going for.
The song slowly turns into what seems like a battle theme for a show or a game, which is quite impressive and sounds really cool. :P
My knowledge of sound mixing and guitars is kind of limited, so other than saying that I didn't hear any audio cracks/clipping or missing notes I can't really comment much on the technical side of things. I'm sure there is someone on the Audio Forum who'd be more than happy to give some kind of analysis though.
All in all I'd say you did a great job, I'm looking forward to seeing the finished product!
P.S
Would you mind if I used this W.I.P as background music for a cartoon as long as I gave full credit? :)