I'm really excited to get 3.5 with JSON mode. Trying to get it to consistently generate JSON has been one of my biggest issues. I've been playing with GPT-4-Turbo's JSON mode, and it works so well.
I found it to reliably produce JSON correctly, but I've found 3.5 to be a poor performer at things like entity extraction and following directions compared to other fast models such as claude-instant (though that does not have function calling).