The very first Dr Who I ever watched (by accident) was her last episode on the series, "Hand of Fear." It was cheesy, and I missed the first part, so I didn't have a good feel for any of the story or the plot. But it was Science Fiction -- British Science Fiction. And the low-budget special effects were endearing (the show was produced in 1976, when the height of special effects was four TIE fighters chasing after the Millennium Falcon and I was watching it in post-Battlestar Galactica 1982).
A few years ago at OryCon, (where else am I going to bump into a television screen?) I managed to catch her farewell scene with a much later incarnation of The Doctor. What struck me was, A) wow, she can act, and B) OMG, I hope I look half as good as she does at... her... age (oh, wait).
What I liked about her portrayal of Sarah Jane Smith was that she was competent without being
- an alien (Time Lord or otherwise),
- Nobel Savage Cheesecake,
- or a Ditzy Whiner.