If the map is realistic (i.e. has the standard terrain...containing objects like mountains, forests, cities, nothing wacky) the colors are not that intuitive. Is red your mountains? Is brown your mountains? What is the yellow (my best guess is farmland)? I cannot figure out what the blue region in the bottom represents - lakes? Tundra?

I don't think the coastlines are too rounded. All maps simplify the areas they represent in some way, and you say these islands are continental scale. Maps on that scale shouldn't necessarily try to show every cape and gulf in the shore. I say keep the coastlines.

Two geographical concerns.
First, if the main islands are very large, where are the rivers? Unless all the land is arid, there must be some way to collect all the runoff from precipitation.
Second, clusters of uniform, evenly spaced islands are pretty rare. I'm trying to envision what the land would look like without the sea there, and it looks like a bunch of mesas, of equal size and spacing, sticking up from the seafloor.

By the way, what program are you using to create this?