This misconception that Murray is boring and lacks personality is a myth gone now, even if this does go on personality alone, without achievements. The only reason there was a public perception of this was because of his monotonous voice. It's fairly deep and only sometimes switches in pitch. Once people got to know Murray as a person, his opinions, tastes and distastes, likes and dislikes ... you could start to see his personality.
It also takes a lot of character and personality to come through what he did against Djokoic after being 40-0 up in the wimbledon final and not closing out the matchpoints, the weight of the countries expectations were so heavy on his shoulders.
For people whom hear Murray for the first time in brief interviews, the perception may be, from an overall "image" point of view (Not looks) image, that he may be a little dull. He doesn't feel the desire to smile when there's no genuine reason and feeling within side him to do so, he's probably the most real person in tennis. However, when something really is amusing or makes him smile, he does. You just need to have him in a natural real conversation, not staged interviews just after matches asking very cliched questions with yes or no answers. Lots of likes and dislikes and opinions.
If anything, Nadal is the player I find boring, not much his game, but him off the court. Very canded, diplomatic (Almost verging on unhonest) cliched and just a bloke on "autopilot". Like the lights are on, but no ones home. Oncourt however, Nadal's disco lights are on and the parties rocking.