I show my colors all the time. When we do things as a guild, it is with colors showing. A group of 6 or 8 people standing in a group getting ready for missions with colors showing, is just too cool. Same with doing missions and quests, all the same capes locked in combat, nothing looks better.
depends on the character---though I rarely use it with my mesmers as I like to look at the back of the dresses.
Some of the armors clip (my monk, my ele) so I dont wear it with them....though my guildee likes to poke me about not wearing it.
I've never been in a guild log enough for the cape to load. It's pretty much "Welcome Noxify" ---3 second pause--- "OKAE KICK NOEW LMFAfaAOAOFAGA!!11!!"
For me it also depends on the armor as I have always loved matching it to the cape though with my current cape I can only wear it on at least 3 characters.
Only if I'm doing something with multiple guildies/alliancies, like a fully manned fow run. If it's just me or my RL friends, I'd rather see all the fancy armor I paid so much for.