Everyone's got their stories about cl but they skew negative I think because few people are going to jump on here and start threads about their legit or happy ending cl transactions.. Not quite as interesting as the "maw of despair" type stories..
I've sold a bunch of stuff including pins on cl as well as buying (always in person) and really can't say I've ever had a bad experience. Some flakes when selling but you just get used to it and it's easier to pick them out.
Regarding Pinside I was signed up for a year before posting -- used rgp until I remembered I had an account at Pinside and switched over. Plenty of lurkers here. I personally am super Leary of shipping but no reason it couldn't work out either..