Got mine in my pocket right now
I prefer to use it for close up situations to do "impromptu" effects. However, when I am doing something big I usually use other prediction methods. Even so, I have put my super sharpie to constant use, and love it to bits.
I've replaced the ink once, I used the innards of another sharpie, and aside from some stained hands, all went pretty smoothly.
The only gripe I have about the thing is that the fidgety bit doesn't always want to come off smoothly. Which isn't really a big deal, just a little annoying. Oh, and it's expensive. Other than that, all thumbs up.
-Ike