Update Feb 26, 2014 - Just updated a machine to 10.9.2, the update that fixes the nasty SSL bug. It does NOT fix this color management bug.
After quite a bit of testing I have come to the conclusion that there is a serious color management bug in Mac OS X 10.9 Mavericks. This is subtle but will result in your shadows being displayed much darker than they really are. The bug affects almost every color managed program and is present whether you use a display profiler such as a Spyder or whether you use the built in profiles. The bug was introduced with 10.9 and is not present in 10.8. So if you are a pro using Mac OS X, stay on 10.8 for now. Strangely enough, Photoshop displays correctly, but it is the only program that does consistently. Aperture plugs the shadows. Lightroom displays correctly in the Library module but incorrectly in the Develop module which makes developing your pictures when looking for shadow detail difficult. I already submitted a bug report to Apple so we'll see if it gets fixed. I am not the first to notice this as is clear from this thread on Adobe's Lightroom forum.
This is the display in Photoshop(correct) on 10.9.1
This is Aperture on Mac OS X 10.9.1:
The first row has disappeared and the second row is much darker than it should be
This is Lightroom Library module (close to correct)
And this is Lightroom Develop (way off again):
Hope this is useful to somebody. The test file came from lagom, which I turned into a RGB tiff file with an included sRGB profile so that Aperture could read it. Again, on 10.8 the display is identical in all software. Also, it doesn't matter whether you calibrate or not or what calibrator you use, they all show the issue. I used a Spyder 3 Pro here but the issue shows up with other calibrators too.
EDIT: This bug is fixed in Aperture. It is still present in Lightroom and Safari
