I've used it since day one with no problems. Aperture 3 is a significant improvement... so if you haven't upgraded, do so as you'll see some worthwhile changes. My only issue is beachballing from time to time on a Mac. I have a MacBook Pro (mid-2009) with dual 2.93 ghz processor and 4 gb ram and it still beachballs when I use the cloning tool for a few minutes. Aperture is a resource hog and the DMR, with 59 mb 16 bit files really taxes the program.
For absolute best IQ I still use FlexColor, especially when I need to print big.