I've just tried iPhoto 4 and it's noticeably faster on my 550 TiBook than the previous versions. Especially with photo scrolling and it doesn't pause for 10 seconds when switching from album to album. I personally don't care about the added transitions for slideshows, but I guess other people might like them. The shared photos thing is cool, as is the organizing photos by year. I would've labelled it iPhoto 2.5 though, I dunno about 3, and I really don't see that many changes to warrant 4. Anyway, I fully intend to get the full package when it becomes available on the 16th.