Well, I have asked it to design/invent three DIY tools that I needed.

One was stupid : it needed a microprocessor etc.

Another was unique - but too close to existing products to offer benefit.

However, one was novel and probably marketable - and took only 20 minutes in a chat with GPT-4 to finalize the design.

Just think how life will be when this catches on : everyone with an imagination and access to a 3D printer will be building all sorts of weird things.