The primary problem with copying the star trek computer is the user interaction. One of the biggest reasons all of the star trek's utilize a voice command computer is ...
For directing.
Otherwise when the crew entered a command, recorded a log, etc. they'd either always be shouting it out or making us watch / read the creation of text. It was quite brilliant from a directing perspective, but do you want everyone around knowing how many times you go to facebook/hacker news/gmail all the time? For that matter, personal log entries etc. Yes it has its place when you're in isolation, but its quite difficult when around others.