I haven't been following the AI space very closely, especially outside of OpenAI stuff. How far behind are open source alternatives? 

I've heard about stuff like llama2 supposedly being decent for chat but I'm assuming the agents/function calling and whatnot is a different story?

I like building apps on web3 protocols. DevRel @ ENS Labs. gregskril.com

API providers (should) spend considerable resources in model quality and tuning so when you use such APIs you get the benefits of all of that. If you just use an open source model you'll need to do more work on your own to get it to do what you want and do a lot of output sanitization yourself.