What kind of support does OSX have for JPEG XR (also known as HD Photo)? I know that there is a Photoshop plugin for it, but are there any other forms of support such as an image preview or other editors that can read/write the format?
The support for JPEG XR in OS X is limited at the moment. Being a technology designed and potentially encumbered by Microsoft patents (although as of last year JPEG XR is a ISO recognised standard and part of Microsofts Community Promise) probably doesn't help its quick adoption into the Apple system.
I think as use increases, support will make its way into all operating systems, not just OS X. But even now, even Microsoft support has been limited with support for the format only appearing in IE9 and Windows 7.