If you want to take advantage of iPhoto's latest capabilities, but don't want to commit your master images to its internal database, there is a way. You can set up a referenced library scenario that allows you the freedom to switch among any non-destructive photo manager -- such as Aperture, iPhoto, Lightroom, and Adobe Bridge -- for the same set of original images. And none of them will alter your originals in any way. It's not an approach for the average consumer. But photographers desiring lots of flexibility might be interested.
In my latest Macworld article, Store photos outside of iPhoto's library, I show you how to set up a catalog of master images on a separate hard drive, then "point" iPhoto to them. Instead of ingesting your masters into its internal database, iPhoto notes their location, then refers to them when you need to work.
There are lots of insightful comments that accompany the article, and I encourage you to read them all. One very important point that comes up in the ensuing discussion is that you should test this method of image management first before committing your entire library to it. But for certain people, this approach allows you to play with new iPhoto features such as geotagging and face recognition, while still having the flexibility to use other applications with that same set of images.