I use mod.rs because I like having a module entirely contained in its own directory, rather than having part of it in the parent one. Obvious exception is when the module does not have submodules.

It also follows the same structure of crates, where mod.rs maps to lib.rs. It has the (minor) advantage that I can trivially extract a module into its own crate by copying the module's directory and renaming mod.rs to lib.rs, but more than anything I like the homogeneity.

But then I don’t really like to have much else in mod.rs other than mod declarations and pub use. Maybe a utility fn or a not-unwieldly implementation of struct “Foo”, the module’s namesake.

Same.

My mod.rs only contains a sequence of pub use self::...;.