I wear whatever I'm going to wear for the day at work - usually cargo shorts or something similar and a polo, bowling or t-shirt. I have an office all to myself and work mostly independently so nobody cares what I wear.

For some it's going to depend on the length of their commute. Mine is only 10 miles round trip so I don't get too uncomfortable. Having recently gotten into longer distance road cycling, there's no way I would wear street clothes on a long ride.

I've never tried commuting in long pants but maybe some day I'll give it a shot. Fortunately where I live commuting year-round in shorts doable.