The only problem is getting the right word in the right place. The accuracy is said to be between 86 and 94 percent. Missing one word in ten is still quite annoying and not a pleasure to change using voice commands. Spell checkers alone are not enough to get the correct words. As An Interface Speech has its pros and cons as an interface.
Speech works better for input than for output.
Since we can speak faster than type, speech has obvious advantages as a means of input. However, we read faster than we can speak and understand what we have read better than what we hear, therefore text is a better method for the transmission of information back to us. Speech as a means of output may be helpful in certain circumstances. It is of significant benefit to the vision impaired or for those away from their monitor. NLP will take the computer a step beyond simple command processing and allow natural language queries.