I like it for either gender, but moreso for a girl.
I have known a few, but not oodles. Various ages, so I don't think of it having a specific age that it's stuck in... though most I'd know would be under 40. Maybe it just was never excessively trendy and lots of people think of other names to use.
I kinda prefer
Robyn on a girl since it makes it clear, but either is ok.