This name is also used in The Netherlands, at least since the 60's. A fair number of Dutch prospective parents were inspired to name their daughter after a main character in a book called "De ongename reisgenoot." [noted -ed]
I'm biased about this name. On the one hand, it looks beautiful and is unique in some sophisticated way. On the other hand, the last syllable "tha" puts me off. So, I like the look of the name but not the pronounciation. I'm going to just stick with Diana or Deanna.