The thing that fascinates me most about the new iPhoto is the Faces detection. It is really amazing. I identified Vanessa in one photo. iPhoto picked up a whole bunch of other possible Vanessa photos automatically, including ones where there were so many people in the photo and Vanessa was just one tiny face in there, or another were her face was smeared all over with chocolate. iPhoto did a pretty impressive job.
The faces detection isn’t perfect of course. There were a few mismatches. Including, ahem, one in which my dad was identified as me. I wonder if we really do that much alike. Hmm or is iPhoto saying I’m looking that old?!
iPhoto can also automatically group photos based on the place where they were taken. This depends on geo-tagging information being embedded in the photos. This isn’t so useful for me right now, because I do not have my photos geo-tagged. (I could, it is something my N97 supports, but I haven’t decided if I really want geo-tagging turned on.)
Other features in the new iPhoto includes integration to automatically upload photos and albums to Facebook and Flickr. It is really convenient to use.