Apple has recently released Snow Leopard, the latest version of the Apple operating system used on Macintosh computers.
As a life-long Mac user, I have purchased the upgrade. But as is my life-long procedure, I am holding off on installing the software.
Some programs, drivers, utilities have not yet been upgraded to work with Snow Leopard, and some may never be.
For instance, Aperture will work with Snow Leopard, but only if you’ve installed the latest Aperture update. I have heard some reports that various printer drivers are not working well with Snow Leopard. Nikon Capture NX 2, Nikon View NX and Nikon Scan do NOT work with Snow Leopard.
For a relatively reliable and current list of compatibility, I’d point you to Macintouch’s list. http://www.macintouch.com/specialreports/snowleopard/slcompat.html
There is another compatibility site here – http://snowleopard.wikidot.com/
In addition to compatibility issues there are important changes to how the new OS natively handles color.
OS X v. 10.6 has switched to gamma 2.2. On all previous Macs, the native gamma was 1.8. This constantly caused problems for photographers who wanted to share their photos online with Windows users who uniformly use 2.2 gamma. This is a good thing in my opinion, but it may change the way your images look to you and require you to re-calibrate your monitor(s).
Apple has prepared an immensely helpful document on the gamma change and I highly recommend all photographers who use Macs take a few minutes to read it. http://support.apple.com/kb/HT3712