I agree with Eld - it seems too uniform. I'd randomize/add more islands to the part in the lower right (which I quite like) and maybe add some small islands here & there. also the undulations in the coast (what i think others might be refering to as zig-zag) are too uniform. For instance, look at the bay of biscay on a european map - its relatively featureless and almost unrealistically straight. contrast that with the islands of the aegean or the western adriatic. different areas, even quite close to one another tend to be radically different.

So just try to break up the uniformity of the coast a bit - some straighter areas, peninsulas, archipelagos, isthmuses and other features.