I tried on those Levi's commuter pants once. They weren't as terrible of a fit as I expected, but they still were cut really straight so that what fit my hips was really big on my waist, and I couldn't justify spending so much money for something that didn't really fit correctly.
Betabrand is working on a women's version of their Bike to Work pants, but it's apparently taking forever. IDK when they'll finally be available.
These look awesome, but the price... ouch.
So in summary, I don't know. I just look for denim with some spandex. More lightweight fabric tends to be more comfortable than heavier denim since the seams aren't as bulky and it usually stretches better, but then there are durability issues.
Leggings or compression shorts under skirts/dresses = by far the most comfortable option for commuting, in my opinion
Edit: I guess you said shorts/knickers, not pants, so that probably wasn't helpful. As far as shorts and capri-ish things go, there are some companies (Lole is one that comes to mind, and their stuff is often sold cheaply on 6pm.com) that make "activewear"-type shorts that look normal but that might be comfortable for riding, but I've only looked at that stuff and still haven't bought any of it, so I can't say for sure.