If you're doing any sort of text editing, you should consider Vim--once you climb the learning curve, you'll be faster and more efficient at everything you do. Also, Vim is my default search/replace tool--whenever I need to make changes throughout a document, most often, I'll copy and paste into a Vim window so that I can take advantage of regexp-based replacements. Vim isn't for the faint of heart, though--it's hard to learn and super complex. If you use a text editor once or twice a month, or just need a simple way to strip out formatting, Notepad will get you where you want to go without all the confusion.
I don't consider the steep learning curve to be a hinderance on the overall usability. I would rate this a ten, but to be honest a lot of people do get hung up at the beginning and just abandon it. However, for people who have made the moderate effort to get over the hump, nothing can be more usable.
The support is somewhat lacking; Vim doesn't really have support outside of its forums. The forums, while notably good, aren't equal to real support though, and the steep learning curve makes you wish there was a help desk that would assist with all of the basic questions. There are several handy books and guides that can be found, and most implementations of the product come with "vitutor" which walks you through its usage.
I think it comes down to usability (and frankly, just preference). There's an old adage that Emacs is a good Operating System with a poor Text Editor! Jokes aside, when looking at different text editors, such as Emacs or Nano, Vim is the one that is usually always preferred because of how simple it is to learn. The learning curve of Vim compared to other text editors just makes it such a natural choice.
