Function-level caching is the best match for how I'd use it. Often the reason for bothering to cache is that the underlying process is slow, so some kind of future-with-progress wrapper could also be interesting. An example of how that could be used would be wrapping a file transfer so the cell can show progress and then when the result is ready unwrap the value for use in other cells. Or another example would be training in PyTorch, yield progress or stats during the run and then the final run data when complete.
