Anyway, when I first moved to a new city, I tried doing the whole 'language tandem' thing, which, by the way, is not a popular phrase in the US. In fact, many people don't understand what that is. People usually call it 'language exchange'. At least in my experience.
Anyway, I used http://conversationexchange.com.
It was frustrating. But it depends what you wanted out of it. I wanted to genuinely learn a language, but had heard a lot of people use it to date.
It didn't work out for me because I was a beginner, and I needed a little more structure. The people who I met just wanted to 'chat', with no real learning material. And many didn't even know what books to recommend.
I think it would've been better if there would've been two people who genuinely wanted to learn a language and were at the same level. But even then, switching back and forth from teacher to student is challenging, especially amongst beginners.
I think it worked out great when both parties had sufficient knowledge to not use a book, and were just learning vocabulary and a small set of new rules.