There are lots of powerfull IDEs and fancy text editors like TextMate. However, old good Vim is still "one editor to rule them all". It's..
- Fast. Vim may be hard to learn, but when you master it, you'll be editing fast, very fast. Typing with all 10 fingers, ultra fast navigation within file, numeric modifier for commands ("10dd" - cuts 10 lines), repeated commands with ".", macros, and zillions of key-combos at your disposal - all this makes Vim by far the fastest editor on the planet.
- Good for health. With Vim you do not have to use mouse at all. Even if you're using Vim's graphical implementation like gVim or MacVim, you absolutely do not need to touch you mouse at all, everything is much easier and faster to do from the keyboard. Considering the fact that you use mouse very frequently in most of other programs, your right hand tires much faster than your left hand. With Vim, you may balance load on your hands - they will do similar things and tire in parallel. Thus, you'll avoid potential right hand joyents problems, which arise from frequent use of mouse.
- Available everywhere. Vim is cross platform. It runs natively on UNIX and Linux. There are also GUI versions, adopted for major operating systems: gVim for Windows and MacWim for Mac OS X, they look and feel like native apps for these platforms. Thus, you can edit files with Vim on your Linux/Mac/Windows system, then ssh to Solaris or FreeBSD server and edit files with Vim there. It is so nice when favourite editor is available anywhere.
- Extensible. Visit vim.org and see yourself - Vim has zillions of plugins readily available to greatly extend it's functionality. For example, vimfiles plugin extends Vim with all of the neat features of TextMate editor (like bundles, project browser, fast file search etc), effectively turning Vim into the best editor for Ruby on Rails programming (as it combines features of both Vim and TextMate). Vim has its own scripting language for extensions, and it is quite easy to create Vim extension yourself.
- Cool! The coolness of Vim is like the coolness of Linux. It is hard to master, but when you do it, you feel like you've just got an elite status, a status which is impossible to gain with money, just to achieve with intellect and hard work. Surely, such kind of coolness is valuable only for geeks and nerds alike :)