I was using whatever the latest Lightroom version was at the time. I started using the 17-40 around 2009-2010 I'd say, and I bought the 17-55 much later, so I suppose that Lightroom support improved in the meantime. Plus the difference was apparent on the camera's screen, with all the controls unchanged between the lenses.
I actually tend to add vignetting in post-processing, so that's likely not the cause. The issues I had were with color rendition, and in particular with subtle variations in tone.
I don't remember there being any strong chromatic aberration either. I remember that both the 17-55/2.8 and the 17-40/4 where quite highly rated at the time, with the former having a better measured quality than the latter, even on a crop sensor.
Don't get me wrong, I don't remember there being any "technical" issues with the 17-55. It was plenty sharp and aberrations were kept to a minimum, especially since I never pushed my luck with strong backlight, etc.
But maybe that's the thing, images were maybe too "clinical". I wouldn't say the pictures were "depressing", they were just... "meh". Like random snapshots. Sharp, well-exposed snapshots, but snapshots still.
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Edit: Regarding editing, I should add that I experimented with DxO optics, which had profiles for both lenses. The corrections were quite amazing, especially at the wide end. But given my usual subject matter, I never considered the change meaningful, so it didn't bother with it in my regular workflow.