I doubt anyone would argue against me calling iPhoto the flagship application of the iLife suite, if only by dint of being the most universally useful. After all, we all take photographs and need to organise and edit them, right?
Last year's iPhoto added Events, which automatically grouped photos based on the date taken. 2009's version adds two new semi-automated organisation methods, Faces and Places.
Faces, as the name implies, uses facial recognition to group photographs of people based on their subjects. The actual detection is pretty good and only gets better as more data is fed to iPhoto. Initially photographs are scanned for faces and marked as an unknown when found, add a name and you can see all the faces iPhoto thinks are the same person and either agree or disagree with the detection algorithm.
Over time this checking process becomes less arduous, as most faces are recognised correctly when importing new photographs. If you're looking for photos of a particular person then you'll be wanting what Apple calls the corkboard, a checkerboard of snapshots of all the faces you've tagged with a name.
Places works on a similar bases to Events and Faces, sorting photos, oddly enough, by location. Primarily this should be done using geotag information embedded into photos with a camera that supports such magic - as the iPhone's does (yes, it is a shame that camera also sucks). Longitude and latitude data are converted into 'real' place names where possible.
Data for adding locations is pulled from Google and if no information is available in the photo, it can be added manually. Strangely iPhoto was unable to tag "TrustedReviews" but "Legoland Windsor" - I have young cousins, okay? - was accepted with nary an issue. Being Google-based, Places browsing boasts a similar browsing method as in Google Earth, with pins appearing above a map surface to show where photos have been taken.
To top off the updates to iPhoto, Apple has also added integration with Facebook and Flikr. In both cases, I imagine this will pretty useful to subscribers to those services wishing to ease the tedious process of uploading umpteen photos to share with friends.
Faces data added in in iPhoto is added to photos on Facebook and, conversely, tags on Facebook will contribute to Faces - the only requirement being consistency of naming. Flikr can make use of iPhoto data, too, being as it is able to handle geotag data. Photos added to Flikr will sync back with iPhoto, too, which is pretty neat - and can of course be disabled if unwanted.
Image editing has been refined in iPhoto '09. Red eye removal now uses face detection, eliminating the need to select eyes in photos, automatic enhancement algorithms have been tweaked to give better results more consistently while highlight and shadow balancing now incorporates tech from Aperture. I wouldn't throw away my copy of Elements in favour of iPhoto, but for the average user it should prove a more than capable image editing program.
Also on the 'new additions' list are Slideshow Themes, which create dynamic slideshows using data from Faces and Places. Images swoop around, noticeable effects including crops applied to portraits where appropriate. These slideshows can be synced with an iPhone, or iPod touch if wanted.
Last, but not least, Apple is now offering a printing service called Travel Books, with iPhoto dynamically creating scrapbook-style flipbook designs, which can be bought from Apple. Pricing varies between around £7 and £20 depending on the size and kind of album wanted - hard cover, soft cover or wire-bound. Having not seen a finished product I can't really comment further.