I've known guys to do that even, and think it's weird. Unless you have like gorilla hairy arms, to me it's just another pointless grooming regimen to keep up with...

i dated a girl who did that. thing was, she was italian and had really thick dark hair on her arms (and elsewhere) so shaving it really did make a difference. but it only was really sexy when it was freshly done and smooth, when it was a couple days w/o her having shaven it was stubbly and nasty...

I knew a girl in 8th grade who did that. But her arms were crazy hairy. Like inch-long hairs before she started shaving them...
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I also know some swimmers that shave all of their bodies -- arms and legs, before a competition to reduce drag...

What happens when she forgets for a couple days? If anything creeps me out it's stubble. As long as she keeps up with it though, I'd consider it "hot". Some women need to, some don't...