Pre Black Friday when I played waaaaay more than now and multi-tabled I used one. But to be honest....I didn't really like it. It distracted me. I focused too much on the numbers and not the situation at hand. That's my fault....I didn't learn to apply those #'s to the situations correctly. Maybe had I done that, I'd have appreciated it more.
Now though...no, I don't and wouldn't. I don't play more than 2 tables any more and I've come to realize that many online players....may not be the same player that those #'s correspond to. Could be a roommate or spouse playing that play completely different to what your HUD represents. That could just be my tin foil hat approach to life though.