I don't know about the glasses, I have only some L lenses, and some others, like the EF-S 17-55.
When the question of "L qualification" came up, the official answer of Canon was, that only a full frame lens can have the red ring. Furthermore, the EF-S lenses don't have the same sealing as the L lenses.
The EF-S 17-55mm is a super lens. I wanted a very sharp wide zoom, so I ordered the 16-35mm f/2.8L II (the new model) and the 17-55mm together, with the agreement that I send back one of them. I tested them a week long with hundreds of boring shots against each other and against the Canon 50mm f/1.4, the Tamron 28-75mm (my copy is excellent) and the Sigma 20mm f/1.8. I compared the fine details in non-demosaiced raw format to see as close as possible what the lens (and the sensor) delivered.
The 15-55mm is virtually equivalent to the 50mm f/1.4 in sharpness, which is the sharpest I had in this range. In the shorter lengths it was equivalent to the 16-35mm, and I stress it, that was the new model. The Sigma is not in the same league.
Disclaimer: I did the sharpness comparisons with f/4.6-f/8, as I am not interested for the performance wide open.
CA is strong in both the 17-55 and 16-35mm (not worse than with my other shorter lenses). The 17-55mm is less prone to flaring; this may be due to the specific hood, which is shaped for the smaller angle of view.
Some examples of the bokeh are here:
http://www.panopeeper.com/Bokeh, comparable with a few other lenses.
If one consideres the IS, then there is no question: the 17-55mm does not have any serious contender. Plus, it is much cheaper than the 16-35mm.
There is one problem reported repeatedly: the lack of good seeling. When zooming out, the lens extends and breathes the air into the inside, unfiltered. Some owners have sent their lens to Canon for cleaning, but if one has to do that repeatedly, one needs two lenses - plus it gets costly after the warranty exiration (and the shipping...). Someone grew tired of that and took the front of the lens apart and cleaned it - and found the source of the problem as well. I will do the same, when it comes to that point.
Note, that the hood has to be purchased extra.