I'm very grateful that the JJ Abrams Star Trek movies have not (so far) made dramatic changes to the Starfleet uniforms. It has always bugged me, the number of times the uniforms have altered over the years, as if the quartermaster's office at Starfleet Command could never make their minds up as to what defines haute couture fashion out on the final frontier.
The TOS designs are simple and have translated well to the big screen. Of course, we've also been provided with a bunch of variations: dress wear, rugged terrain wear, etc. Still, they have always returned to the basic look in the end - the one established by William Ware Theiss.
Yes, it's because of Theiss that you got to see Nichelle Nichols' legs every week! As the TOS costumer, Theiss had his (non-union) seamstresses operate out of a secret apartment near the studio where they toiled throughout the night to make the clothes. It goes without saying that he had a mandate from Gene Roddenberry to make all the women as sexy as possible, especially the guest stars.
Did you know Theiss was a three-time Oscar nominee? He worked on, among other films, Harold and Maude and Bound for Glory, plus uncredited work on Spartacus. He would go on to win an Emmy in 1988 for Outstanding Costume Design for a Series for - you guessed it - TNG.
The 25 most out-of-this-world TOS costumes