One of Tidy's biggest strengths is its portability. Versions of Tidy are available for over 15 platforms, including Windows, DOS, Mac OS, several flavours of UNIX/Linux, and BeOS. On top of that, Tidy is an Open Source application. If there isn't a version for your favourite operating system and you program in C++, you can download the source code (the building blocks of a program) and start hacking.
Tidy is also integrated with a number of text and HTML editors, including NoteTab Pro and HTML-Kit (for Windows), as well as Bluefish and Quanta (for Linux). And this is literally just the tip of the iceberg. Several other editors have also integrated HTML Tidy, and you can even add Tidy support to a growing number of editors.
Being a command line tool, Tidy won't appeal to anyone who is used to point-and-click convenience. You can, however, create a batch file or shell script to execute Tidy with the options you commonly use. The only other downside is that you sometimes have to run Tidy two or more times to completely clean a file.
All told, Tidy is an indispensable tool for any Web author. It can save you a lot of time finding and correcting errors in your HTML. And it can ensure that your Web documents comply with standards. Just for that reason alone, Tidy is worth the download.