Before moving to iPhoto I was using Windows Live Gallery to manage my photos. One reason that I liked Windows Live Gallery over the older versions of iPhoto is that it had face detection. This allowed me to identify people in my photos.
Another reason that I liked Windows Live Gallery, is that it has native flickr support. Since I do use flickr, this reduced the number of tools that were need to handle my photos.
Unfortunately, the integration between Windows Live Gallery's people tagging an flickr support is missing something. When I usethe flickr web interface, I tag photos with a tag for each person that is in the photo. Since Windows Live Gallery supports taging photos with the names of the subject people, and arbirtary other tags. When you upload photos to flickr, the string tags get added as tags on flickr, but no flickr tags get added for the people identified in the photos. It would be great if I can enable Windows Live Gallery to create a flickr tag for every person identified in a photo.
iPhoto '09 has the same features that WIndows Live Gallery had. Now that I am using it I will tests to see if Apple has implemented the functionality that I have described.