It's been said that Tomiki sensei sometimes used to train in three-piece suits. He would just come into the dojo and start training. O-sensei did the same as well. There are some nice pictures of him doing self defense in a dockyard. Lastly, there are some self-defense techniques illustration in one of Shioda sensei book all done in officeware.
I've trained at times in street cloths and found it did not really affect my training at all. Then again, I was wearing combats and a t-shirt at the time so they were comfortable and lose clothing. I've even trained outside and ukemi is fun on grass but not so fun on asphalt -- it burns.
Now, the _real_ question is do you pick cloths (and footware) to wear based on whether or not you can do Aikido in them?