I know I am a newbe, but still I would like to share my experience.
I used coinmixer.net for about a year now, sometimes they pay out slowly after 24 hours or even 48 hours, but they always did as promised.
I got nervous when I read this scam message and I just tumbled some coins and my payment got delayed, but i received my tumbled coins.
they might be selective scammers. I did about ten transactions, all under 3 btc, and all went well, except some delayed.
sorry for bad english.