I don't really see the relationship between Dumbledore and Grindelwald as "lovers." I see it as more of an infatuation with him because he finally found someone his own age that could match his wits and his intelligence.

As for how the actors will do, that remains to be seen, as I have not seen either of them act. Going to see New Moon when it comes out but it doesn't seem like he does much in that movie (just sits on his throne). Maybe I should see Sweeny Todd.