...and I think the only money I regret spending is on a 70-300 (non-L) because that lens was SO soft at 300mm.
+1, I wish Canon would update this lens with the features (non-rotating focus, Ring USM) and build quality of the Tamron and Nikon equivalents. The 70-300L looks like a great lens, but is much larger and more expensive. I have also considered the 70-200 f4L and f4L IS, but neither will fit it my current bag (I know, not the most valid excuse, but I like my current bag). I have considered going back to the 70-210 USM and/or 100-300 USM I owned previously (I love their focusing speeds and the IQ from both almost exactly matches the 70-300 IS). I can't complain, though, I got the 70-300 IS for a song, and could easily sell it for a profit. I'm just bitter because I've used the Nikon 70-300 VR (released 2006), and enjoyed the experience much more than the Canon (released 2005) lens I have. I think Canon owes it to it's 6D customers to have some reasonable-quality entry level (read: non-L) zoom lenses, and currently they have zero in the UWA and normal ranges, and three relatively mediocre tele zooms. Yes, the 24-105L, 24-70 f4L, 17-40L and 70-300L IS are great lenses, but they are not in the same price range (un-kitted) as Nikon's 24-85 VR, 18-35 and 70-300 VR. Entry-level consumers (and purchasers of used 5D's and 5D Mark II's) need more choices for their cameras without taking the 'L' plunge.