First off it is FOSS (Free and Open Source) and available for Windows.
Additionally, it is a very mature project, currently on version 5.6.8 (at the time of this writing), and therefore contains no major bugs or missing features.
It has far more features then I know about and far more then I want to write about. Additionally, it has a plug-in feature that allows anyone to make extensions to the program. So suffice it to to say, if you want a feature it most likely already has it.
Some of the more notable features are:
- Support and ability to convert between: Windows, Unix, and Mac files in many different encoding formats
- Intuitive and powerful find and replace functionality
- Support for (syntax highlighting, auto-completion, etc.) over 40 different programming languages
- Tabbed interface
- Macro creation and use
- Fast and reliable
Now all of these features are great, but they are just icing on the cake. What I want to stress the most is how easy to use Notepad++ is. While it can be used for some very advanced things, that does not make it any more complex to do the simple tasks.