- __getters and setters__.

The point of declaring an element private is to restrict an access to it. Providing an unchecked getter and setter (as `getNext()` and `setNext()`) defeats this purpose. You may as well make `_next` public.

The real goal of restricting access is to help the client to not mess things up (a scientific term is *maintaining an invariant*). I don't see what invariant is maintained by `_value`. The `Node` class doesn't really care what value the node stores; it is the client code that does. A `_value` getter just complicates client's life.

- Sorely missed are __iterators__. Their absence locks your class out of the STL algorithms library. A client would have to reimplement everything that STL provides for free.