Very very linear. Quite interesting experiment actually, although I'd like to see some big battle zone somewhere. Because the way it is now, a terran taking one position and sieging up there is almost unbeatable even with superior forces.
Also you should just run (yeah just run) a couple of time the map. Just have an unit and tell it to go to the other mainbase with only one click, and see if it does. try around if there are any situations where units get confused by the long dinstance.

very appealing for the eye, and I think it's not your first map ;)

but anyway, the small mainpath will cause balancing problems, as panschk pointed out

Will making an alternate path around instead of just the giant 'S' help? Cuz I'm picturing slow but hard tank pushes all the way to the other base...

don't think so actually :/

to have this map balanced, you'll have to change it into a quite normal airmap, like with this large s-shape in the middle as expos to fight for...

I use scmdraft, too btw
I resize with irfanview

oops, last comment to wrong map

a bit changed...added some bridges round the mid...it kinda leads into the nat , so basically the swirly s path is just an extra way around with some expos