I just read three or four reviews on the G5, and they all say the same thing, this is a great upgrade from the G3. Never knew this but the number 4 is considered unlucky in Japan hence the G5 name.
From what I read i was impressed with the 16 mega pixel sensor , it's improved ISO and it's 6 frame per second rate, all of these things will give you better macro shots . If the reviews are correct and I don't doubt they are, this will be a fine addition for your set up
There is nothing worse than a sharp image of a fuzzy concept.. Ansel Adams