Legacy applications already on VFP are a good candidate. If you plan to move to iOS and Android apps, VFP is not for you. Also, in future access to VFP programmers may be limited. You could use VFP as a powerful database tool. I know of many programmers who love to exploit the features of VFP to create easy to use applications.
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.
Although MS has discontinued support of VFP there is a good community of programmers that are available for help. In fact we have several programmers at Apptread that are skilled not only in VFP but also .NET so that if there is a need to migrate some parts of applications to .NET , it is easy for us to do that.
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.
We are only using FoxPro because it is the only way to add custom plugins into the software we use to manage our stock. FoxPro is a semi-oriented object language and should clearly not be compared with recent technologies.
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