Result.toOption has return type Option<'T>. The idiomatic/canonical notation is 'T option. The use of Option<'T> here means that Option<'T> shows up in code/line lens and tooltips all over my codebase when using this function, whereas I would prefer 'T option.
I haven't checked, but I am guessing that this could apply to other functions in the Result module, too.
For completeness, note that the same kind of issue would also apply to functions typed with List<'T> instead of 'T list, and other similar types. (I haven't checked or encountered any, though.)