Do you have the ability to keep clothes at the office? If so, you could bring in clothes once a week, and then just carry a small backpack for your lunch, etc. For a 33 mi. round trip, I'd rather ride a road bike, and wear the full roadie kit.

Personally, I don't have a problem with wearing office clothes with a helmet and clipless shoes on my bike, but I only have a 4 mile direct route. But with your distance I'd be more concerned about prematurely wearing out the seats of my good pants.