In particular, I want to single out the fourth season as a moment when the show really does hit the right note every time. This is the season that includes the Old Who meets New Who Death of the Doctor (watch it yourself - Part 1, Part 2), Katy Manning returning as Jo Grant (now Jo Jones, of course), Finn "Loras Tyrell" Jones as her grandson, and David "William Hartnell" Bradley as an evil vulture alien. There's a view that Matt Smith is at his absolute best in this story; he's certainly at the top of his game, and everyone is brilliant.
Without being too snarky, one of the strengths of Season 4 is that Tommy Knight, who plays Sarah Jane's adopted son Luke and is frankly the weakest of the regular cast, gets shuffled off to Oxford in the first episode and appears only occasionally thereafter, leaving the field to the much stronger Daniel Anthony as Clyde and Anjli Mohindra as Rani, plus of course Lis Sladen herself as our heroine. I still miss Yasmine Paige, who played Maria in the first series, but it's a strong line-up. The fifth and sadly truncated final season brings in twelve-year-old Sinead Michael as another human child created by aliens, adopted by Sarah, and she shows promise; though the best story of the three is the middle one, The Curse of Clyde Langer, where poor Clyde finds that he is rejected by everyone, a brilliant evocation of teenage isolation. (NB that Clyde's mother is played by an actress only eight years older than the cherubic Daniel Anthony.)
It's a shame that the Sarah Jane Adventures never quite got the wider fandom traction that Torchwood did - and I include myself in that criticism, having watched only a few more than half of the stories first time round. They do catch the sense of adventure of Old Who well, and they are comfortingly familiar in format for us old school fans, with roughly half-hour episodes and cliff-hangers. And they remind us old 'uns that we were right about Lis Sladen and Sarah Jane back in the 1970s, when so much else has changed since.
Where might we have gone? Luke was gay; Ace would have reappeared; the giant spiders were toyed with but discarded.
While we're on the subject, I also want to praise the ten Sarah Jane audiobooks, which are surely the only range of Who spinoff audios which made it into double figures without a single duff entry. Eight of the ten were read by Elisabeth Sladen, the last two by Daniel Anthony and Anjli Mohindra. They're a great way of passing a CD-length of time, especially with fans or potential fans of the appropriate age group.
I'll leave you with the last minute of the last episode broadcast during Elisabeth Sladen's lifetime. You may find you have something in your eye at the end.