Normally, I would consider a system preferences app too minor to include in a review, but OS X's deserves some recognition. OS X's preferences tool exposes a surprising amount of configurability, and has very good tools for network and firewall configuration. Certainly, it is more powerful than GNOME's spartan configuration tool. However, it exposes its functionality without ever making the interface seem cluttered or hard to manage. Given its excellent organization, Spotlight integration seems a bit redundant, but it's a nice touch. Overall, it's a perfect example of how beautiful OS X applications can be. The slick Platinum title bar blends nicely into the main window. The layout is precise, and everything seems like it is in the proper place. The window changes size smoothly as required to contain the widgets within. Clearly, a great deal of attention went into making this overall excellent preferences application.
One of my favorite apps on OS X is TeXShop, a front-end to the TeX typesetting system. TeX is a markup language, like HTML, that is extremely powerful and well-suited to writing everything from scientific articles to novels. It is, in short, everything that Microsoft Word aspires to, but knows that it can never achieve. TeXShop is a sublime front-end to a number of different variants of TeX, notably LaTeX and ConTeXt. Its interface is simple and elegant, certainly deserving of the design award it won from Apple. At the same time, it exposes a great deal of power. It has large set of pre-built templates, for generating the code for things like tables and figures, a macro editor, and good AppleScript integration. It does tag completion, brackets-matching, and spell-checking. In all, if I was stuck on an island with a thesis to complete, TeXShop is the one application I would want to have with me.
Another app that I couldn't live without on OS X is Aquamacs. Aquamacs is Emacs with a native Carbon GUI. Its integration with the OS is fairly good. It uses the standard top menu bar, but doesn't have a native-looking preferences panel or have native context menus in the editor windows. However, it has excellent support for native OS X shortcut commands, which means that the app is completely usable without having to learn Emac's horrid and user-hostile shortcut sequences. Aquamacs also integrates with an Emacs package called SLIME, which turns Emacs into a top-notch Lisp IDE. SLIME, in turn, integrates with an excellent Common Lisp system for OS X called OpenMCL, which features a fast, native-code compiler, good code generation, and great error messages. Similarly productive environments for Lisp development are available on other platforms, but the Aquamacs/SLIME/OpenMCL combo is the first one I've found that combines the significant virtues of running on a UNIX platform, integrating with the host GUI, and being free.
Aquamacs and SLIME
I hate to end things on a depressing note, but I need to say a few words about another application I use regularly, Matlab. Matlab, in its Mac incarnation, sucks. Of course, it sucks on every platform, so that is not too much of a complaint. Matlab is an X11 application, and very clearly clashes with the rest of the platform. It doesn't use the top menu bar, preferring to it an in-window menu bar. Matlab is an eclectic mix of a main program using a custom toolkit, and add-on programs using Java's Swing. The latter are rather buggy, and are brain-dead from an interface point of view, but are made tolerable by OS X's good Java implementation. One thing Matlab brings out, through no fault of its own, is the uneasy truce between the CLI and GUI worlds in OS X. OS X's GUI/CLI integration is not nearly as good as it was on BeOS. The UNIX filesystem looks quite different from the Mac one, and it is always confusing to use Matlab, which has a mixture of both by virtue of having its own file browser as well as using the standard OS X file dialogs. On the point of GUI/CLI integration, OS X is definitely inferior to GNOME on Linux.
Matlab and X11