The thing about Toshiko and Owen's deaths was that they did in fact die for something. Not to be too over the top but it was heroic at least, whereas Ianto's death turned out to be pointless in the scheme of things. If I see a reason why, I can mourn the character's passing but reasonably adjust to being without even if I'm a fan of the actor (eg Dom's death as Charlie in Lost) Ianto's death just left me with the feeling it was done for a 'SHOCK! OMG!' factor rather than anything else which is a waste of Gareth David Lloyd's talents. If he had to die, it could have been given more meaning, in my view.