Thanks guys. Great feedback! I'll try to get around to tweaking this today, before putting in the superficial details like cities and whatnot. It was very much a learning experience - I followed a very fine couple of tutorials, but I suspect I screwed up some of the sections (pretty sure the mountains aren't.. meant to look like that) and I might have gotten the colouration a bit wrong (I'm having issues with.. gradients). I think I could tweak the contrast on one of the layers a bit to cut down on the blotchiness. Hmm. I'll have a play and put the results up.

Thanks again!