The XMLSpy JSON and XML Editor from Altova is designed to give developers the tools they need to build the most sophisticated applications with its graphical schema designer, code generation, file converters, debuggers, and profilers for working with XSD, XSLT, XQuery, XBRL, and SOAP.
Altova XMLSpy is an excellent tool for creating/designing new XML schemas (XSDs) using a visual layout tool and helps developers and architects work with XML and JSON documents, understand and validate and diagnose issues with XML and JSON documents. It is not well suited for working with other data formats, such as YAML or CSV.
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