Water is a frame-rate killer for me. I can handle hundreds of parts. I can handle the re-entry effects. These things barely faze my computer. But the water... oh god. Water destroys my framerate. Launches must be done with the camera facing towards the sky. Plane flying is tedious and painful. Even in orbit around Kerbin, the lag makes docking and other maneuvers frustrating. I've already changed some of the config settings to help with that, but there is still some lag from the oceans, and now they look lower than they actually are, so things end up floating in air, instead of on the surface.