I think book reviews would be a great thing to use Wiki for in the library. I like to know what others think about books. It would also help to read the reviews to be able let patrons in on what others think about certain books.
Wiki would also be a great way to organize library events. Similar to what was done in the tutorial about camping. Staff might be given a certain aspect of the event they are supposed to do and you can have an area for what needs to be done and an area for what has been accomplished.
Would I use Wiki's professionally and personally? Probably from time to time.
I did my Wiki on favorite vacation spots and i enjoyed reading about others favorite locations.