It's so interesting to read everyone's point of view about MIL and DIL relationships. I've just joined, having come onto the site because of my frustration, sadness and bewilderment 
My experience has been going on since my 15month old grandson was born. A few not so nice things are:- my DIL hasn't phoned me or come over to see me once in all that time and they only live 10 minutes from my home. She tells my son what she expects me to do, which is more or less nothing, as she sems not to want to encourage my relationship with my grandson. As my user name suggests, I think being a grandparent is very special. My mother died when I was 18, so as a mother and grandmother, I didn't have an "imprint".
My son does his best, but DIL prefers to send her son to nursery 3 days a week, rather than the original 2 planned and 1 day with me. There are many other little niggles, but on the plus side she is a devoted mother, makes all his meals herself and was very patient with her premature baby. I've tried to be in her shoes, but don't think she's been in mine. It's so sad, as I've never had my grandson in my house on his own and often feel like social services are monitoring me when she's here. Probably we've never been close, but it's far worse now and as I hardly ever get the opportunity to talk to her, she can't say I'm interferring!