As a small post-mortem, one interesting thing we learned while building this library: The reason Apple never included a read/write lock.<p>They're hard to get right (probably not a problem for Apple), and their overhead usually counterbalances any potential performance gains (possibly a problem for the unwary developer).<p>We've got some optimization work to do :-)
I love that Objective C/Foundation provides a distinction between mutable and non-mutable collections and tends to favour the latter. (I also hate they make it impossible to test which a collection is.)<p>Pet peeve: "insure" is used on the page. For some bizarre reasons Americans use that word when they mean "ensure". The difference is very important - insure is when you don't want something to happen and ensure is when you do!