CoffeeCup Software offers the CoffeeCup HTML Editor, an HTML and CSS text and code editing option, featuring free and paid versions with more advanced features.
My typical use is to edit HTML and CFM pages from prior projects, and use them to create new ones. So, I rarely use the tools for designing pages provided in this application. I have found the ability to preview a page very useful. I am aware of numerous features in this editor, that simpler editors would not provide. It has proven to be a great fit for my use.
I would recommend Vim in any scenario where text files have to be viewed, created, or edited on GNU/Linux computers. Regardless if you need to quickly change a few things in a configuration file, or you need to write up a full document, Vim is great. I wouldn't use Vim to view, edit, or create anything that requires "rich-text". In other words, if you need to format the text (bolding, font colours, word-art, etc), then Vim isn't the tool to use.
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.
There is no commercial support for Vim. Thus, it will not get a mark beyond 5. However, community support is very good. You can easily find solutions for most of the problems in the community.
Vim's keybindings are a lot more complex than Notepad++. With that, comes a whole bunch of capability that Notepad++ just can't match. Emacs is comparable, in terms of capabilities--because Vim is built into so many unix systems, I chose to learn it instead of Emacs. Knowing both probably isn't a bad idea, but there's enough to learn in either camp to keep you busy