I think I've heard once or twice of someone that uses and like Marvelux, but I can't count high enough to the 'number' the people who have used it and dislike it.
Dave Campbell has written a fine, short, simple, cost analysis article and posted it on his website about casting boolits. I was disturbed to see a well positioned container of marvelux in the leading photo ...to each his own.
http://davecampbelloutdoors.com/pouring-bullets/