Roelof Brouwer, Thompson Rivers University
I use only J for trying out algorithms that I develop in the field of soft computing. Like a J user said "J is great for trying out crazy ideas quickly". It means that when the algorithm is developed it can be executed and avoids the need for a programmer saving a cost and most of all saving the time required for explaining the algorithm to a programmer. A co-researcher once remarked " how did you code this algorithm up so quickly".
I also use a pseudo J as a notation in my publications. It is pseudo in the sense that when a mathematical equivalent exists I will use it rather than a J primitive. So far no paper has been rejected because of my use of J.
The articles listed on my home page all include either APL or J. I stopped using APL when I converted to J in about 1995. Therefore publications after about 1997 are J based.
I also introduce students to J in my algorithms course and have the students use it as a prototyping language in some other programming courses. It is great for students to check the results of a program written in another language. I have even introduced the students in a computer literacy course to J.