I have one I picked up for my kids to use, and it's great for what it is, and for the cost; but in a direct comparison to any of the L lenses, it doesn't hold up.
I like the images you posted, but with the possible exception of the lizard one, they're not very sharp (that being said, they are small, and it's tough to judge). Which is to be expected of that lens unless stopped down to f8-11 or so. Bokeh is also really nervous, and AF is slow and tends to hunt. None of these things make it a bad lens though. I own one, and it was worth EVERY penny. But to compare it to the 70-300L or any of the 70-200s and try and say it's a better lens, is just not true.
I never, EVER said the existing lens was as good as the L's optically. Only that it was very good for what it was, and if they made any improvement to the optics it would be even harder to justify upgrading to an L for most buyers.
I'm glad you like the images. I know they aren't perfect, but they show off the lens very well.
The snake (which I admit exhibits a very small amount of camera shake) has VERY narrow DOF, centered on its eye, and there isn't a lot of detail there to resolve. (It was shot at 250mm, f/5.6, 1/10 sec exposure, handheld, through glass, at essentially minimum focal distance.)
The lizard and the baboon in full size both exhibit clear single-pixel level detail, though shadows on the baboon suffer because it was accidentally taken at ISO 1600 in relatively bright light. (all three were taken with 450D/XSi)
(See, I can pick my work apart as well as anybody...)