I agree with the extra utility of fast lenses. I'd point out, however, that speed is not so essential in every lens you own. I have both Contax and OM systems right now, with four to six lenses each. Most folks would probably want a f2.8 80-200 zoom in their bag. These large, pricey lenses are the photojournalist's friend, offering immediate versatility. But in more casual/slow-paced work, I can easily get by with my f4 zoom in that range. My Tokina RMC cost $50, not $500 like a used OEM 2.8 version. That's augmented with a 135mm f2.8, a lens that's fallen so far out of fashion that they're practically free. (Tonight I auctioned a clean Yashica 135 2.8 for a whopping $29, and made a profit. I got it for free as a throw-in when I bought a few old Takumars in a pawn shop. My other YUS 135, which I'm keeping, was $8 at the thrift store.) So I find that I often need a fast telephoto or a zoom, just not always at the same moment. They don't need to be the same lens. If I need the extra stop for my child's sports and theater performances, I can crop from the 135mm's image. If I was shooting slides of travel or landscape subjects and needed to crop in the camera, f4 usually is fine. I do have a Tokina ATX 80-200 2.8 that I use on rare occasions, but that's a bargain too. I got it for $60 because it's infested with fungus. I'm careful about pointing it it at light sources, and it does a fine job, too