Also I gave a shot to a 3D dock I can not say that i was very happy (3d-Space VFS). I mean indeed it good but really uncomfortable to use. In fact until you open an application it is a lot faster from the normal dock.
Third Issue. Last night I connected a "NORMAL" monitor to my ibook and using ScreenSpanningDoctor I put a movie on the monitor and in the same time I was working on my website on my ibook. and also working on some animations. Everything worked great and still get some free memory.