Like in all genres, there's good and bad chick-lit, and of course that's completely subjective..
I, for instance, found The Nanny Diaries just terrible, one of the worst examples! (sorry!)... and I find Marion Keyes good. I also thought Bridget Jones was good - for the genre. But I would never compare Bridget Jones's Diary with, say, To Kill a Mockingbird.
I don't believe in looking down my nose at any genre per se, but some genres are certainly lighter than others; that is, they are more for a relaxing, distracting time and for readers who aren't looking for any major reading challenge at the time. When I'm looking for that sort of book, I'll choose chick-lit over, say fantasy or horror.
If there's a demand for a certain genre, then publishers wil fill it, and there's no point getting upset about it. What disturbs me about the whole chick-lit phenomena, however, is when it merely reflects the shallowness that seems to be taking over that generation of women. Clothes, make-up, getting a man, dieting - Lord, is that all life is about? That's why I like Marion Keyes - she writes in a lighthearted way about these things, yet manages to get through to a deeper vein. I just hate shallowness, in whatever genre.