Exploring GPTs: ChatGPT in a trench coat?

Simon Willison reviews OpenAI's GPTs, custom ChatGPT configurations announced at DevDay, and says his first impression was that they were little more than ChatGPT in a trench coat, though more time with them revealed more capability. He describes a GPT as a named configuration with instructions, up to four conversation starters, uploaded files, toggles for Code Interpreter, Browse and DALL-E 3, and optional API actions. He notes that GPTs can only be used by $20/month ChatGPT Plus subscribers, which limits distribution, especially since Plus signups are paused. His highlights include the Dejargonizer, which explains jargon in pasted text, and JavaScript Code Interpreter, which runs Deno in the sandbox. He also reports that the Create tab overwrote his hand-written prompt for the Add a Walrus GPT without asking.