Bearing in mind I haven't seen STID so I don't know how well the reveal was handled, I thought the 'teasing' got a bit tedious, at least for fans.
PR dept: "There a super-sekrit villain surprise in STID!"
Fans: "It's Khan, isn't it?"
PR dept:"It's an awesome surprise!"
Fans: "Yeah, it's Khan."
PR dept: "Nooo, Cumberbatch is playing John Harrison, tee-hee!"
Fans:"Guys, we know it's Khan."
Karl Urban: It's Gary Mitchell! Oops, I totally leaked the secret!"
6 months later:
Cumberbatch: "My name is Khan!"
Fans: "No shit, Sherlock."