During takeoff, the TO/GA pitch mode commands 8* nose up until airborne. When airborne, pitch commands change to the lessor of 15* nose up or slightly below the PLI.
As climb rate increases, pitch commands change to maintain the MCP IAS/MACH window speed plus 10 Knots. This speed is V2 for takeoff.
However if you do not perform a text book rotation and maintain the desired pitch attitude exactly for more than 5 seconds are more, the speed will settle on the MCP +10 to a maximum of V2 + 25. This is the case usually with me when i am flying, but as i like to tell my FO's, what is a few knots between friends.
My company uses V2, but as Boeing designed the acft. for V2+10 , so there is no need for using any other speed than calculated V2 according to Mr. Boeing.