I joined in 2005 when my second child was a year old, on the recommendation of a RL friend (we knew one another's usernames, and knew various other women on MN).
It was more 'school playground' back then, in that there were the cool girls and cliques who derailed threads with endless in-jokes. I was a nobdie, obviously. But it was also acres funnier and sharper, and the grammar and spelling were better. Huns and fools got very short shrift (rightly so, IMO).
The thing I am most sorry about is that pretty much every thread now has "lighthearted" or "trigger warning", because people have become so wet that they need to have it flagged up when someone is not being entirely serious. That's the thing that I find most annoying about MN now.
Other than that, the conversations are pretty similar to how they've always been. Though I think women's standards are generally lower ("My DH shags around and goes out every night and drinks and has debts, but he's an amazing Dad"), which is a shame.
There were some people who gave reliably good advice, too, though any reliably good advice on here now is drowned in a sea of huns and pathetic friendship/wedding dramas.