OK, it definitely doesn't work reliably.
starting with VS.exe not running.
From cmd.exe, I run 'vs file1.txt'
SLick starts and loads file1.txt.
From a 2nd cmd.exe, I run 'vs file2.txt'
A 2nd instance of Slick starts and loads file2.txt
This doesn't happen everytime, but often enough that it is pretty easy to repro.