Are there any hills or lakes on the planets?
You should release the standard map with the high-detailed models, and offer the low detail ones as a replacement pack.
Also, you should put a transparent sphere the color of the atmosphere of the planet around each planet so it looks like they've got an atmosphere. For example, the Earth would have a transparent blue sphere around it, Mars would have a transparent orange atmosphere, etc. Mercury or the moon would have no atmosphere. You could keep these sphere's fairly low detail.
Oh, I'll get to work on your asteroids, don't think I forgot about them. I've just had some other stuff to do.
Are you still having problems with your gravity zones?