First off the bat, A FlyGirl, that was a great post, from the few posts of yours that I have had the privellage of reading you are a rolemodel for all F/A's. I agree with the general tone that passengers dress should be comfortable as well as neat. Their are some pros and cons to dressing well or dressing messy on planes that I will try to outline below
Fancey Clothing: (designer garments) Pros: You look nice and you get to show off (sorry thats my immature side) Cons: If wearing really fancey clothes as I have seen, espcially in F class on what I call short Longhaul flights, like from BOS-FRA or JFK-LHR, one runs the risk of ruining their clothes during the flight. An even greater risk that these people run is to become Paraniod about their clothes becoming dirty. Im sure all us FF's have seen someone keep a watchfull eye on your drink as to make sure if doesnt spill. Or the ones who really spread the napkins out thin to protect their clothes. What I am trying to get at here is the worst part about dressing up on a flight is not only the discomfort but the constant worry about your clothes and the effects it has on those seated around you.

Smart Causual Dress: Pros: Normally comfortable, easily replaceable yet elegent enough to show that your not on the airplane because you won the pig in the polk gameshow Cons: I welcome replies in this area.

Sloppy Dress: Pros: Comfortable, easier to sleep and haslefree. Cons: Sadly IMHO their are F/A's out their who are alot less understanding than A FlyGirl who might be slightly more inclined to give better treatment to those who dress cleanly. Thanx for you time and have a good one