Dev Chair : My love-hate relationship with Apple development
Whether you love or hate Microsoft, you have to give them credit for popularising programming on Windows. While I was a junior programmer fresh out of college learning C++ and working on train control software, truckloads of CS/Engineering graduates were learning to program in Visual Basic. Whatever faults VB has, the way it allows even beginner or causal programmers to learn the craft and produce quick and dirty applications means that programming for Windows was no longer the eminent domain of the traditional CS/Engineering graduates, where FORTRAN and C/C++ rules. Microsoft continues this trend with C#/VB.NET and the .NET Framework, providing a lot of built-in functionality that used to require hand-crafted code or expensive third-party libraries, freeing up developers' time to concentrate on problem solving instead of mechanics.
With OS X, Apple began with Objective-C and Java as the programming languages of choice but ever since version OS X 10.3 Java had been put onto the back burner and is expected to be phased out eventually. Unfortunately, making Objective-C the sole language of the platform also makes it difficult and 'expensive' for Windows programmers, such as yours truly, to join the party. The difference in syntax (despite the 'C' in the name it does not have much resemblance to C or C++), difference in framework and API, difference in IDE philosophy, and the lack of refactoring tools (ReSharper, CodeRush, etc.) and unit testing tools (NUnit, JUnit, etc.) mean that some of the more open-minded programmers (mostly Java and .NET) will not take an active interest in Apple software development.
The upcoming Xcode 3 looks like it would make a big step in closing the gap, but the IDE still lacks the tools mentioned above to attract the time-constrained, less hard core developers from the Windows side of the world. The dark horse may be the combination of Eclipse IDE and Mono project. The Eclipse IDE is mature and has a flexible plug-in architecture so refactoring and unit testing tools can be integrated into the IDE by third party developers. Meanwhile the Mono project has been making lots of progress as far as compatibility with Microsoft's implementation is concerned. And the ability to take code written in Windows and runs it in Linux or OS X (with some limitation, of course) will appeal to Windows developers, at least as a starting point.
In fact, Eclipse/Mono may actually achieve what Sun tried to do with Java all those years ago. Remember 'Write once, run anywhere'?