Hmm. It's a bit of a scattergun article - I think linking the 'I don't know how she does it' film to MN (and to her daughter's education) is all a bit muddy. I'm happy to admit, I don't want to go and see a film of the book because I find it hard to sympathise with the dilemmas of a very wealthy professional mother. And you can find plenty of threads on MN about 'how to manage nannies/domestic staff' and other 'luxury' dilemmas.... so I see where she's coming from in that respect...
That said, you can also find, if you look for them, threads that are not just political, in the way that she mentions, but are about stillbirth, bereavement, infertility, mental health, that carry a huge emotional weight and are invaluable for the people who use them.
The whole middle class thing.... well, MN does feel very middle class to me. Before anyone gets irate - let's remember, online forums need you to be (a) online, and (b) literate enough to type clearly. The most deprived and excluded mothers in UK society don't tend to have internet access at home, nor can they all type and express themselves like a graduate. So you won't find them here discussing their problems.
I think it's as well to recognise that, whatever you think about it. Personally, I can't stand seeing a MNetter mocking some 'netmums' type poster with 'hun' and 'lolz' and mispelling for comic effect etc - it's bullying snobbery, and from grown women, it's fucking grim.
That aside, do I think in that MN is broadly skewed towards the lives and problems of the mostly middle class? Well, yes. It's all very well saying it's open to all mothers from all backgrounds, but in practice, that's not how it works. Do I think that middle class bias is a problem? Not sure. Except when it becomes crowing at the less literate and less well educated. Then yes, it's bloody horrible.