In the early seasons she definitely was the source for all non-medical science. She kind of lost that when her lab was blown up in, I think, The Alternate.
Not that she ever seemed to use her lab much. She then seemed to become a character that the producers wanted to use for character development. We learnt a lot about her past lives over the course of the series, in episodes such as Equilibrium
. And it's pretty obvious that as soon as Worf turned up she became his counterpart so that his Klingon side could be explored. Once they were married it really did seem as though they reached the end of the road for the character.
As far as it goes with Terry, I never disliked her as an actress. I thought she did a great job with the material she was given. The less said about her hairstyle in The Search