There isn't a lot of difference. It's mostly speed optimizations. I have a crappy video card, so I had to optimize until it ran smoothly for me.
On the first demo, in some areas, it had over 40,000 polys drawn. I've got it to where there shouldn't ever be more than 12,000 drawn at a time. Oh, I also added a slight fog to this demo.
I'm sorry about the trees. I haven't had time to put them in yet. But if you get clear to the other end of the map, there is one tree surrounded by a whole bunch of robots. I'm using it as a temporary place-marker for the end-of-level teleporter thingy.