I usually wear button-up shirts (and sometimes a sport coat) when going out or meeting with clients, but I am a firm believer that neckties cut off blood flow to the brain.
Also, slacks are just not comfortable. I much prefer a nice pair of dark, well-fitting, ironed jeans.
I don't often wear dress slacks, but when I do they feel more comfortable than my usual khakis or nice jeans. Hm...maybe I should wear those dress slacks more often.
Seriously. Good pairs of slacks are about as comfortable as you can get in any situation. Part of the genius is the variety in materials that go in. You have everything from lightweight, super breathable pants perfect for the summer (when jeans and even khakis become miserable in any humidity) to thicker wool trousers that will feel comfortable even in the middle of a blizzard.
That said, the peak of summer comfort is seersucker, but I won't even don that often because it does make you look like an anachronistic dandy.
Also, slacks are just not comfortable. I much prefer a nice pair of dark, well-fitting, ironed jeans.