Yeah Paul, I find the aperture a problem with this lens only when shooting deepsky, but for close up's of anything else it's actually not bad.
I'd love a Canon ef 70-200mm f4 'L' lens
I've heard it is a fantastic lens for astrophotgraphy.
I guess that I am so used to using prime lenses, a canon 50mm f1.8, and the 85mm f1.8, those are excellent.
I'd love to see a shot with the 'beercan'
Keith..