Its not bad for what it does, organize photos. It's really designed to be a simple tool for organizing and sorting your pictures. But also to help Apple sell their photo books, etc.
I found that if you have lots of pictures, its really more of a pain than anything. When I got over several thousand pictures it got really slow even on my 1.42ghz mini.
I prefer to just keep all my photos in a folder organized by content manually. At least I know whats there when I need it.