Armpit hair is a must, especially if you are well-built. It deepens the recess caused by your pectoral and lat, making you look even more impressive. I wouldn't feel a man without my pits.
On a woman, it would depend. It would take a pretty impressive woman to deliberately not shave her pits as a statement of her pride. I'd want a woman that proud. But if it was from social retardation or simple negligence I'd pass.
Women with armpit hair != hippies. Having said that, I do shave mine, simply because I feel it's more hygienic and a prettier sight when it's warm out and they're exposed. I'm fine with men having armpit hair so long as it doesn't stick out everywhere even when their arms are down. Long armpit hair = no.
Before I post my thoughts let me check myself to make sure im not being biased. Err, I have nipple hair, but its not a lot, and its easy manageable. I also have hair from my lower stomach leading downwards. I shave my genitals and pubic hair though. That's the way my... tutor?first?teacher? taught me, and thats how I've kept it. "I want you to look good naked, and you want me to as well, right?" Armpit hair, yeah I have armpit hair. It's not crazy like 8 crazy nights though. lol. It's manageable, but I run every day, and I'm pretty sure that if I shaved it I'd chafe like hell. Not gonna happen. And I dont(luckily) have back hair at this point. On a side note, I shave my arms. Have been for the past 8 years now, and I wont stop. It's just one of those things I got into a habit of doing. I also shave my face, but that, as well as the above mentioned is because of hygiene. I simply look better clean-shaved.
I really think hair, where-ever, goes with how the woman wants her man though.
Now, on a woman. Nipple hair = no. Armpit hair = Not even if your that prideful/impressive. Down south = If its nice, and not a damned jungle, then fine. I keep mine nice because I want her's nice too. Back hair = Is this possible? moustache = Uhh, hell no?
However, I've met guys who look at it differently than I do. I keep myself in good shape, and I keep myself looking good, and I prefer my woman to do the same.