I am a 28 year old wife, not a mother yet, but I feel I should respond as a child whose mother was a STAHM and then went back to work. I honestly feel like her going back to work was the best decision for her and the family. She was a STAHM until both of my sisters were grown and moved out, but I became a latch key kid at 11. The adjustment was tough, I am not going to lie. The first few weeks I kept forgetting my keys more often than not, but after a while I learned and now I never lose or forget anything, let alone my keys. It was during those years that I also learned how to cook and do laundry, and as a teen when I couldn't get a ride to the mall, I picked up a bus schedule and got there myself.
Compared to my older sisters, I had an easier adjustment into college and taking care of myself. I planned a trip to London by myself and have driven across the USA all on my own. My parents never worry about me taking care of things, and although I am the youngest, I am usually thought of as the most responsible and trustworthy sibling, whereas my sister cannot take a train from Providence to Boston by herself.
My mother was also happier during that time. She made friends and had interesting stories to share about her work day. To all the STAHM's out there, I am glad that my mother was home to care for me during my younger years, and if it is feasible for you to do, I would encourage it. But I honestly attribute a large part of my personal growth to my mother going back to work. Sometimes being a good parent means letting them go to find their own way.
I asked my teens last night for the honest to God truth. They said they loved going to day care. It was a good one and they had a lot of fun there. They also said they would definitely send their kids. I told them that if that was their plan then they would need to get a good job because it is expensive.