Here's a question for all you Mac-ers out there: What's the best way to build desktop software for a Mac?

My company Aperio has built a high-performance spiffy image viewer for very large images used in virtual microscopy, particularly Pathology applications.  This is currently a Windows desktop program, written in VB wrapping a C++ OCX with C++ supporting classes.  We're planning to build a native Mac version of the same program.  I believe the C++ supporting classes will port directly with a bit of codesmithing, including the ones which deal with image files and network communications.  However the higher-level stuff will have to be rewritten from scratch.  So what do people use?  Java?  C++?  Is there a technology similar to ActiveX controls which readily enables embedding functionality into other programs?

If you have thoughts on this, please email me.  (I plan to post everyone's replies, so please tell me if you don't want attribution for your thoughts...)  Thanks!

[ Later: Here's the answer...  thanks, everyone. ]