By far the best thing is that he makes his own playdates. I'm not the middleman anymore. He just makes plans and asks me if it's ok. And if his friend doesn't have a landline, I let him call their parent. It surprises them, but when he leaves a message, they love it. He's definitely had more time with friends because of it.
Another funny thing was he complained about writing a thank you note, so we said "OK, the alternative is that you have to call them". He called them, had a nice conversation, and thanked them. Honestly, it was better than a thank you note.
It's been one of the best purchases we're made. I feel some hope this will delay the eventual begging for a smart phone because he's able to do the most critical thing, connect with friends.