A final feature worth noting is Facebook notifications. Beyond iPhoto, iWeb is another place that Apple has joined the Facebook bandwagon, allowing the software to automatically post a link to your site whenever you make changes. It's a nice touch, though perhaps not the most necessary feature, since sharing a link on Facebook is pretty simple.
If you're a Mac user and use even one of the iLife applications, chances are that you'll find at least one new feature worth the US$79 cost of upgrading to iLife '09. Most users will find that iPhoto and iMovie combined are an incredible value. If you or a member of your family is interested in learning the piano or guitar, the basic instruction offered in GarageBand itself is more than worth the price, considering the cost of lessons or self-instruction books and DVDs. The one caveat is that if you have an older Mac, you should verify that you will be able to run the features you want. Though iLife '09 will run on many recent Macs -- a G4 Mac running at 867 MHz is the base requirement -- it does require an Intel Core Duo or higher Mac for some features such as Learn to Play, or a G5 or Intel Mac for others that are part of iMovie '09.
All in all, it's an upgrade that for most users is going to be well worth the US$79 price.