Generally I've struggled to find language partners who can commit to regular times, me included. This is why I always book a teacher because I know they will commit to me and because i've paid I'll commit to them. However I have met some interesting and helpful people in the language exchange, the exchanges just haven't lasted long, one exchange actually turned into a paid teaching opportunity for me which was great!
I had one awful experience with a guy who I very patiently listened to for 30minutes, made a few corrections and was generally very encouraging towards him. When it was my turn to speak French, he spent the entire 30 minutes laughing at everything I said. At several points in the session he got up and walked around his room not paying me attention to me and talking to me from across the room! It was very unpleasant and awkward. I blocked him after the session :(
My worst languages exchanges have been with young people, they are always extremely nervious which force me to play the role of a teacher, guiding them and leading the conversation the whole time.