I'm a huge Doctor Who fan and so I decided to give this show and Torchwood a try. This one beat Torchwood by a LOT. The writing is almost as good as in Doctor Who, the acting is very impressive for some of the young actors in it. I love all the characters, which I can't even say about Doctor Who (I hated Rose in the second season).
If you're looking for something to replace Doctor Who while it's not on, this show is perfect. But it really stands on its own. It doesn't keep tying itself to the Doctor Who universe (except in a few stories, I will admit). It's got more heart than Doctor Who, while Doctor Who might be wittier and more dramatic, The Sarah Jane Adventures is witty but it's also sweet. You'll feel like a kid watching this but in a good way.
It makes me ashamed to be an American, quite frankly! If BBC can produce a show aimed at preteens and make it so incredibly good that it has an audience of all ages, and yet America has crap like Hannah Montana... well CBBC must be superior.