That was the beta version !!
I'm running 10.5.4 on my Macbook Pro, and I have to admit, i did not like it over 10.4.11 first it came out, but after the 2nd update, I'm loving it. It's fast and stable ... never crashed on me, Never.
I'm a photographer, and am using Aperture every day ... it's working just fine.
I have Kalyway on my Dell desktop, but I never run Aperture on it ... so maybe it's not as smooth as it supposed to be on real mac. Just maybe