Installed without problems on a 3 y.o. 15MBP and a new iMac. See no performance issues so far, but I HATE the fact that the FULL SCREEN photo viewing is no longer there! I just hate it, that there is absolutely no way to view pictures full screen. period. (this was THE MOST important feature of iPhoto.) As such, zooming in full screen is NOT available anymore either, instead of floating windows with adjustments, etc., zoom, effects, you get stupid permanent bars that you can't even move anywhere. Also, gone is ability to quick launch a full screen slideshow. You are now asked to select photos for a slideshow first, and then create that slideshow. In Classic you will get an ability to view these full screen, thats the only way. The stupid music that accompanies classic is ... well, stupid. I just wish the Apple store in Bethesda MD had it installed so I could see how horrible it is, before giving them $79 for a Family Pack! My money now goes to Adobe for LR3, a much, much better suite! Forgot to mention, this version is NOT 64 bit, and it does not recognize dual-screen mode either, something that Adobe implemented years ago. Shame on APple for dummifying a simple photo viewer to the iPhone level.