I commuted for years with a cape in to Naval Station Norfolk and it was a bit tricky fishing my ID out to show the gate guards. Apparently there weren't many other cape users because the Marines just started waving me in after a while.

I recently started using a Carradice again and it works great. I took it on TOSRV and I stayed cool and dry while my ride mates were constantly stopping to put rain gear on and take it off. Another cool thing you can do with a cape is when it stops raining you throw it up over your shoulders and quickly air dry.