Yes, nursing a baby is good for a writer. And I'm not talking about my son. I'm not going to wax eloquent on how good nursing is for a baby's brain or claim that he'll be a writer someday. Nursing is good for me--for my writing.
Don't get me wrong, nursing is very time-consuming, and that's hard when one also has a toddler to keep track of. When Zaxxon was a baby I preferred to take him to the rocking chair in his bedroom for nursing. It was quiet and comfortable, and perfect for a mommy who still felt really uncertain of the whole process (not to mention in pain for many more weeks than the experts said I should.) With Kal'El, I haven't had that luxury (so it's a good thing that I already know what I'm doing this time.) I've nursed him all over the house whilst trying to keep Zaxxon entertained. BUT... whenever somebody else is occupying the toddler, and always for the last feeding before bedtime, I still like to sit in the rocking chair, which is now in the living room. And of course, I have a good book with me.
And that is the point I'm making. Since nursing takes up so much time, and it's mainly just sitting still and letting the baby do his thing, I've gotten a lot of reading done. I read out loud, too. I figure it's good for my son to hear my voice, and it helps him to hear the language.
I use the time to read stuff I've always wanted to read but haven't had time for: an anthology of stories written by my old professor, the first James Bond novel, a short Connie Willis book, the rest of the stories in Doomology (yes, it took me this long), The Time Machine, The Island of Dr. Moreau, and The Invisible Man. Reading classics (and not-so-classics) is always a good thing for a writer, because the more you read, the more you expand your horizons, and the more you grow.
There are a whole bunch of other books in our library--including titles by Jules Verne and Isaac Asimov--that are on my list, although they've been put aside for now. This is because I've replaced reading them with reading the first draft of my novel to Kal'El. I've never read my work out loud this early in the editing process before, but it's not as painful as I feared it might be.
No matter how busy we are, slowing down and sitting with a good book can be beneficial, and nursing has helped me do this regularly again.