I know (albeit only from looking it up just now) that
Joon is not an alternate spelling of
June, but rather a different name that happens to sound the same.
I love
June, and think it fits all ages, so since
Joon sounds exactly the same I think the same about
Joon.
It's hard to say I don't like
Joon, again since I love
June and it sounds the same, but I don't care for how
Joon looks at all and I think it would be so frequently confused with
June in an English speaking country that it would be a headache. I could understand, though, if someone wanted to use
Joon instead of
June because of the origin and meaning.