I purchased my first Mac at on a Blue and White at version 10.0.x. I did so because it looked like an awesome development platform. Over the years, I discovered that was not the case. Even after moving up through many other Macs, I have consistently come back to trying to develop on a Mac and it just does not work for me.
For doing complex Web development using Tomcat, Apache and a ton of DHTML, I have found that Mac OSX is just not user friendly enough for managing all the different tail windows, process start stop windows, code windows etc.. to build complex apps. The window management is to cluttered to manage so many tasks. I am not a fan of using IDE's and prefer to use programmers editors and standard open libraries. On Mac, the only way to use Progammers editor and edit multiple sources at one time, was to have many windows open. In windows any decent code editor has tabs to manage opened files. It has taken mac almost 8 years to get this right and now finally some editors support tabs. I think KDE is now finally including MDI frameworks OOTB but Gnome still is not so same issue there.
Another huge issue with development in Mac OSX is the inability to effectivley extend Finder like you can in Windows with windows explorer shell extensions. The ability to trick out Windows Explorer shortcut menus with tools like File Menu Tools and Tortoise SVN make it amazingly powerful development system. This is a problem of the Vanilla consumer base of Mac systems and is a huge problem in my mind. I am absolutely spoiled in windows with the dozens of tools I have extended in Windows Explorer. Linux has shell extensions but lack a ubiquitous file manager that crosses all apps which makes shell extensions less valuable to users. Hate to say it but Microsoft did the right thing when it comes to Windows Explorers ubiquitous nature in windows.
To make use of my Mac, I now use VMware Fusion running Windows and this has made me way more efficient by orders of magnitudue than using Mac directly. Windows on a Macbook is often better than Windows on a Windows laptop. Call it comfort level but I am always cursing my Macs when doing deveopment with stupid things like not being able to resize a window in the top left corner.
Don't get me wrong, I own 3 macs at home and am typing on a Macbook pro 17" right now but I do very little development on it unless through Fusion running Windows XP.
Hopefully some day, that will change but for now I have to be pragmatic and just pump out the code in the environment that is the most effective for me.