oh yeah...
A get_index method. If the keys are sorted in a rank structure, it may be useful to be able to determine what rank $last_name happens to be.
This could be because no one is using it or because it does everything anyone wants
I have only used it once (several months ago) and it did everything for me. I know of a co-worker that uses it pretty frequently -- I will refer him to this thread and see what he might have to say. All the feedback I can give you is that direction switches would be quite useful. Don't really know about peek -- never needed to.