I wouldn't call it a swinger site, for me Joyclub is just a place for all the sex hungry folks who want to keep up with the scene. Depends of course how one defines the word "swinger".
It's the best way to find out what's happening in Germany's sex clubs/events as a whole.
Also a great in a sense that registering via Joyclub to events gives you discounts for the entry fees, and it's free to use as well (unless you want to register as a premium member which gives you few extras but isn't worth the price in my opinion).
I haven't contacted anyone via that site but i've gotten few messages after the parties from some ladies who have wanted to keep contact/thank me/etc. If you want to send messages yourself to someone, you need to pay.