this lens: the Canon 24-70mm f/2.8L USM? I'm thinking of upgrading my lens to something sharper. I'm now using a 3- or 4-year old Tamron 28-300mm f3.5/6.3 on my 300D Rebel. It's been a relaible, serviceable lens, but I always wish my images could be sharper. I reviewed my collection of favorite shots from the past few years, and found that most of them were taken in the 28-70mm range, except for candid head shots of people at parties, picnics, etc. I searched the Internet and read reviews on this lens (until my head hurt), and they've been favorable for the sharpness, color, and contrast. Although most mention that this is a heavy lens -- 2.1 lb. vs 1.3 lb. for my Tamron. Might make me use the tripod more often, which is certainly not bad, just incovenient. Before purchasing the lens, I thought it would be a good idea to see if any of you have any opinions on it. Thanks in advance.