EF-S L would be brilliant...
If it was a 4.0, or a 2.8, or dare I say, 2.0 (for those that don't mind regular L heft).
The EF-S 17-55 f/2.8 is already L quality as far as optics are concerned. It's just missing the tank like build quality and weather sealing.
Does anyone know why Canon has avoided making EF-S "L" lenses? Do they figure that most APS-C consumers don't want the added weight, so they stick with a plastic build?
I think its more that the L is linked to their high end lenses for use on high end dSLRs... IE: Full Frame.
EF-S can only be used on the crop sensor bodies, and not the full frame, soooo, yeah, it goes out the window there.
"High End" is subjective.
Sure, they need to coddle us FF users, but some of the crop deficiencies can be remedied with good, fast (.95) glass.
Instead, they make 900 different 3.5-5.6 lenses.
MFT will quickly swallow up all of the amateurs and semi-pros if this practice continues.