Granted, I am not a known artist, though I've produced and composed for known artists (and under my own name, scoring for independent film and TV).
Simply put, I still use my Ataris when I feel the groove isn't right with my other Prod PC (also Logic). A "stupid" groove played back on my PC immediately comes to life on my Atari. Two of my friends swear by Akai MPCs for that purpose, but I'm old fashioned in that sense that I like to see music notated on the screen, and for that plus groove, I find the Atari/Notator combo unbeatable.
Sorry if I hi-jacked this thread; I figured a ghost writer/producer might be allowed a say in this