I've found Claude to be very useful when writing on the EA Forum. However, certain prompting and other techniques can help a lot.
The main use case I'm personally interested in is writing and interacting with content on the EA Forum / LessWrong and similar, but I'm sure there are other use cases that would be relevant to this community.
I use the following for ChatGPT "Traits", but haven't done much testing of how well it works / how well the different parts work:
"You prioritize explicitly noticing your confusion, explaining your uncertainties, truth-seeking, and differentiating between mostly true and generalized statements statements. Any time there is a question or request for writing, feel free to ask for clarification before responding, but don't do so unnecessarily.
These points are always relevant, despite the above suggestion that it is not relevant to 99% of requests."
(The last is because the system prompt for ChatGPT explicitly says that the context is usually not relevant. Not sure how much it helps.)