I suspect Paul is right, few people will have problems with faster performance.
I did have a problem with a TC74 sensor when I optimized I2C bit-bang. This sensor is limited to 100 kHz I2C.
Still it is hard to believe that a factor of thirty in execution speed of basic I/O functions will not cause problems. That is why I designed my optimized functions to get a compile time error rather than revert to the slow functions.
I guess my experience in embedded control systems where predictable api execution time is important doesn't apply to the Arduino.
If Paul is correct then there should be only one digitalWrite and not several under bar variations.