The main problem with (GNU) APL for me is the line editor: I can't feel comfortable using a REPL to write a program without keybindings like ctrl-a, ctrl-w. Everytime I try to learn APL I eventually give up.
As poor as this video is (and the last time I posted it I believe I said I was going to make a new one), it does illustrate some of the features: https://www.youtube.com/watch?v=yP4A5CKITnM
I don't know if this is helpful for you, but I map <c-p> to run the open buffer in Vim in the buffer's filetype's interpreter (or compile and run, etc.). For GNU APL, this is: