I think Federer will be dispatched by Murray if he plays him in the final, it wouldn't surprise to see something similar to the Olympic final if they meet.
Nadal is the only one to really worry about even with his sketchy grass court form these last few years, the man is a beast plain and simple, still would give Murray a decent edge on the grass though, you have to really looking at previous grass court form and the way they are playing on it right now, Nadal is dropping sets already not that it will really mean much if they meet in the final.
Murray has it over Djokovic in slams lately, don't see any reasons why that won't continue in the semi (if the both get there), straight set wins for Murray the last 2 times they have met on grass, obviously can't take him or Dimitrov in the quarters lightly but if Murray keeps up this form he will be ok.
Murray has been taking the piss out of these opponents so far, today it looked like he was toying with matey in some of the points, its noticeable that the weight has gone from his shoulders, you can see it in his demeanor, hes walking that bit taller and just looks very confident.