In 35mm, the range I most use is 35mm to 105mm; I never take action pictures, or pictures in any other situation where rapid framing/change of focal length is neccesary. Zooms have a max. aperture, size, and weight penalty, as well as the performance penalty. Show me a zoom which gives the same image quality as my Nikkor primes, with no weight or aperture penalty, and I might consider it. As of now, such a lens doesn't exist.
My Canon zoom is pretty damn sharp, however it certainly wouldn't match the weight requirement that you're talking about, of course it is going to be heavier because of all the additional glass in order to hit all of those ranges, however if you added up a 70 and 80 and 90 and 100 and 135 150 and 180 and a 200mm and put them altogether that would be much much heavier
~Stone | "...of course, that's just my opinion. I could be wrong."~Dennis Miller