While I would have preferred an Emperor, RotS Obi Wan, Jedi Luke, or a Stormtrooper, we have to remember that Sideshow needs to spread out their core charactersand there is a MASSIVE fanbase for EU characters with little product (especially high end) available.
Whether we like it or not, sex sells. Check out the Marvel thread and see that they make "Black Queen" instead of Jean Grey/Phoenix and it sells out immediately.
By releasing Darth Talon, Sideshow is doing three things: targeting a fan base, spreading out core characters, making a 'sexy sith.' From a business standpoint, tossing in less common characters every once in a while is a great idea (I own Asajj). The problem is when Sideshow stops listening to fans altogether; which I don't think they are doing in the Star Wars section.