I have to disagree that babies will be miserable in WDW. Like I have already posted, my daughter was very happy on all 4 of her trips, at 12 and 15 weeks, 6 months, and 9 months. On the first 2 trips I know she was happy because she didn't cry once, on either trip (well a few minutes on the place on the way home from trip 1 because it was turblent and I put her in her carseat and she wanted to get out, she always hated her infant carseat). Now she didn't really cry much at home, but she would cry from time to time, mostly cause she wanted my attention and I had to do laundry, dishes, or one of the many other tasks I do at home each day. At WDW she didn't have to ask for my attention cause she had it 24 hours a day. She was held in a Baby Bjorn most of every day when we were out (she wasn't a big stroller baby at that age) and was never int he sun when we were in the parks. That's right, she was totally shaded at all times we were in a park and we took many, many breaks from the heat and she nursed whenever she wanted to, and all those wet diapers everyday reassured me that she was well hydrated.
It is true though that those 2 trips were for me as they were planned before I was pregnant. The other 2 though, at 6 and 9 months, were planned for my daughter. We went to DL at 6 months on a convention with my mom, when I otherwise would have stayed home if I didn't have a child. She loved it and had a great time with the characters, watching the Electrical Parade, and going on rides and in shows. She also loved watching the other little kids, since she doesn't see many at home. The trip at 9 months was planned when I thought about how much she'd like the Osborne lights and Christmas parades. My husband couldn't take any vacation time so I went alone with the baby (my husband did come for the weekend, so we had Sat and 1/2 of Sun with him). She had a blast. I travel alone with her frequently to meet my mom at a destination (either at her home or we also went to Las Vegas with her) so that wasn't a problem and everything we did while there (except for the Santa photo, which was for me) was for my daughter. We watched every parade, some twice, and I do not like parades so that was in no way for me. We skipped any ride I thought she wouldn't care about and just rode and rerode ones she likes. The only thing we did for us that trip, and not our daughter, was when my husband was there we ate at the CG. As it turned out though, my daughter liked that too-not only did she love tasting my meal, but she loved watching the fireworks. She'd jump up and down everytime she saw one and squeal with excitement. So when we unexpectedly went to Orlando after a cruise from Ft. Lauderdale we ate at the CG since we knew our daughter liked it. (Now the cruise was for us, not the baby, though she did have fun, but due to problems the ship had, we couldn't disembark and missed our flight, having to drive to Orlando for a flight the next day). We got there early so we had to time to go to MK for a bit (we have APs and happen to have them on us form the last trip) and we rode the Carousel and Snow White. Wouldn't have been my first choice, but Madison likes them so that's what we did.
So I really don't think that you can say babies are miserable in WDW or that it's selfish of parents to take them there. No, my daughter won't remember these trips when she's older, but I will and we've got lots of photos. But if I were only going to take her once, then I'd wait till she were old enough to remember it, but since that isn't the plan, why not take her while I have the opportunity to? She has fun and I have a great time watching how happy she is.