I have to say, after trying it, it doesn't seem anywhere near as slick as the iPhoto version. First of all, the auto-pan effect "pauses" at the beginning and end of the playback of each picture, during the transition to the next picture. It should really Auto-Pan right through the transitions, as iPhoto/iMovie's does.
The performance of it isn't spectacular either. I don't know if it is trying to render the effect at too high of quality or what, but on my office machine, it sometimes stutters a little bit (and I have a pretty powerful machine all things considered). It doesn't ALWAYS stutter, but it certainly does occasionally. The stuttering is mild (not in-your-face) but it looks like a video with a low frame rate. Not buttery smooth. Maybe it just needs a healthy dosing of motion blur...
Also, I too had issues getting it to work.
When I first enabled it, it didn't do anything really. I always have my settings set to Scale large images to display. When I first enabled Auto-Pan, it didn't do anything at all until I manually zoomed in. Then, when it switched to the next picture, it seemed to turn off (or so I thought). I disabled the Scale large images option, and then it seemed to work, but weirdly. It seemed like my playlist would "stop" whenever I turned it on, and refuse to go to the next picture.
After I stopped and started the playlist again, with Auto-Pan already enabled, it then worked properly (and regardless of the Scale images setting). It now seems to be working properly, so I don't know what the story was with all that weirdness, but the very first time I tried it, I was all confused and discombobulated. As I said... it is working now, but the "first glance" was a bit rough.