I've never talked to anyone who didn't like it. Still not sure why it vanished. Too low of a profit margin maybe? Too expensive? I was a kid so I barely remember it other than ordering it every time and giving up the option of getting a kids meal (and a toy!)
I ate almost every night during play practice in high school, or when I stayed after to work on the paper. I think they got rid of it because it was just too expensive to produce vs. how much they were selling. I don't recall what the price-point of it was but it was obviously a bit higher than everything else on their menu. But, man, it really was a good sandwich.
Wikipedia says the failure was a combination of an ill-advised marketing campaign and the burger being too expensive.