It can be a place where women feel safe to share their frustrations with the men in their lives. I don't have any problems with this.
Sometimes, this can spill over into generalised comments about men, and women who have a problem with men in general can feel safe to express those views - and it can become, at times, a very hostile place for men. When this happens, it's fairly predictable that men will react - I certainly do - after all, women react when there's hostility towards women on other sites, and understandably so.
On the other hand, over the years I've posted here, many other posters have commented that they appreciate a man's perspective.
It is very similar to some parent/toddler groups, and often groups of mums outside schools - where I (and other dads) have often experienced hostility, as we're seen as disrupting what for some people is a woman's space that is very often used to talk about relationships, and criticism of individual men is a part of this.
The irony of all this is that the criticisms of men tend to focus on men being inadequate or inconsiderate as parents, but there is a dynamic among women that actively discourages men from being more involved as parents. One thing, for example, that would help men be more competent as parents would be if men felt comfortable on the mumsnet board.
I have always been assured by the people who run the site that it is open to all, despite the name - some women here clearly think that this is a women only space, but unless there's been a policy change, my understanding is that this is mistaken. To be honest, it'd be pretty much impossible to avoid having men on the site, as it's open to the world via the net. As a public site, whatever is posted is visible to the world, and while it may seem like an intimate club at times, it's perhaps wise to remember that anyone can read what is read.
Like I said on another thread - I run a website for dads, and women are more than welcome there.
Finally, I'd like to apologise to Mum2boy - I am like a bear with a sore head at the moment. I won't go into why, because it's very easy to identify who I am and for things to come back to me irl, but your generalisation about men epitomised the hostility men can experience here and I saw it when I felt my wife was being very inconsiderate to me. So you pressed all my buttons and I reacted. Reposting it was an attempt to create a space where your issue was discussed, as it became pretty clear that my post had hijacked the thread, and I tried to make a helpful comment, but that clearly irritated you further. But others have interpreted that as arrogrant on my part... it wasn't meant like that - it was an attempt to separate the issues - meant well, but perhaps mistaken.