Talk me out of the 70-300mm L IS

The price of the 70-300L certainly means there are numerous cheaper alternatives out there. However, I bit the bullet and am very happy with it -- I do not reget the investment -- love the size, sharpness, range, speed of focus, and the IS is "simply fabolous" Outdoors I find the aperature ranges perfectly acceptable.

I upgraded from the 70-200L f4 non-IS to the 70-300L for wildlife use. The IS is fantastic, and the image quality and sharpness is as good as the 70-200L. Its a tad heavy for long treks, but the keeper rate and quality are excellent. I just took mine on a trip to the jungles of Borneo on a 7D, and am very pleased with the results - but I certainly wouldn't want anything any heavier for jungle trekking. Take a look here: https://picasaweb.goog​le.com/kngreen/Borneo#

Quick example:

Sirrith wrote in post #12456776
Doesn't the 70-200 f4 IS's build quality remind you more of the 55-250 than the 70-300's extending front?

I don't think either lens deserves a comparison to the 55-250.

I think about the 70-300L occasionally, but I don't get why Canon made this a variable aperture lens with 5.6 at the long end - just like their consumer zooms. I'd find it easier to justify the "L" premium if this was just a bit faster, say a 4.0 or 4.5 fixed aperture, or even a 3.5-4.5 variable aperture. Maybe "someday" this might not matter due to higher ISO cameras, but for now it still does.