iOS 9.3 is coming in the Spring and will introduce Night Shift as well as a number of other new features.
Snow Leopard Application Incompatibilities Compiled
Apple today posted a support document outlining which applications Snow Leopard will consider incompatible and either sequester or prevent from opening in order to prevent instabilities from being introduced. Several notable applications, including Parallels 2.5 and antivirus software from both McAfee (VirusScan 8.6) and Norton (NAV 11.0), are removed during the Snow Leopard upgrade, which sequesters the affected applications in an "Incompatible Software" folder on the user's system. Other applications, including Parallels 3.0 and older versions of Apple's Aperture, Keynote and AirPort Admin Utility for Graphite and Snow, will simply not be allowed to launch on Snow Leopard.
Users upgrading to Snow Leopard will also see a number of printer drivers upgraded to Snow Leopard-compatible versions, and Apple has posted a second support document outlining the list of printers with compatible drivers available either on the Snow Leopard install disc or via Software Update. Apple plans to update the document as additional compatible drivers are released.
A number of users have also taken compatibility assessment into their own hands, developing the publicly-editable Snow Leopard Compatibility List at Wikidot, which offers an extensive list of software tested by users. The site has been extremely popular with users over the past few days, so much so that the entire Wikidot site was brought down by traffic to the page, forcing Wikidot to disable Ajax on the Snow Leopard site in order to help reduce the load on its systems.