This thread really made me think. 99% of my travel is for business, but I like to be comfortable when I travel. I realized as I thought about this though that I do have habits (not good probably).
1) You can tell if I am coming or going by how I look. When I head to a client site, on my flight there I am well put together, business casual, makeup, jewelry all the adult trappings. After being there two or three weeks I am so ready to get home and so sick of hotels (and often sick from breathing hotel air for weeks) that I am dressed as a schlep when I fly home. Jeans, sweatshirt and a lot less fuss and muss. So the same applies to how I arrive at the hotel!!!!
2) Time of day changes how I dress too. I am NOT a morning person at all, so if I have to be the airport at 5:30 am I do a lot less prep than if I have a 10 am flight. The later in the day my flight is the more dressed up and fussy I am with what I am wearing. Again the hotel gets whatever I flew in.
I do not think this affects my upgrades on flights though, since most times when I am upgraded it happens before I get to the airport and they cant see if I am schleppy or professional looking. Not to mention also I spend a lot of time on CRJ's so it is irrelevant.
As far as hotel upgrades - no I dont think it matters. I have arrived in sweats and still been upgraded and in very dressy and not been upgraded. It is truly the mood the desk staff is in.