I'm personally not a big fan of the Universal Translator... I would prefer it if non-human species just spoke their own languages with subtitles and folks just had to learn to be multilingual, like in Star Wars, Lord of the Rings etc. Heck... even humans have multiple languages! I find it difficult to imagine that the entire Vulcan or Klingon races would have just
one language. In Middle Earth there are various different dialects of each language, e.g.: there are various kinds of Elvish tongues such as
Quenya and
Sindarin.
Okay - so even if one were to suspend disbelief and accept the notion of a circuit that conveniently translates languages... why would their lips move as if they're speaking English? Even the
Star Trek Wiki entry on the Universal Translator states,
"Were the device real, it would more likely have an effect similar to watching a movie dubbed into another language."