Thanks OP for sharing your experience.

I, too, think many people who post on the DIS gloss over the bad, ugly, or disappointing moments of their trips (with or without toddlers).
It really helps to read posts that don't shade the truth, therefore, there are less unrealistic expectations that your WDW will be totally magical every minute of the trip.
We took our DD 2 /12 years old. She is usually extremely well behaved, calm child at home. She was out of her routine and thus not herself on the trip. We went in early May to avoid the summer crowds and to have a bit of a break from the heat.
1. For one, she would not ride in the stroller! We rented a two person stroller from Disney for her to share with her brother. We thought she would like being with him and more comfortable using it. We ended up carrying her the entire trip. I was exhausted but prepared for this since she has a rare disorder and did not walk or put any weight on her legs until she was two.
2. She was worn out and run down after just a couple of days, even though we went back to the room for mid-day nap break.
3. She had a major meltdown one day as we were heading into MGM. We even slept in late that day and did not arrive at the park until around 10:30 or so just to help her since she is a late sleeper at home. The following picture tells it all.
4. We had lots of trouble finding plain white milk for her to drink in the parks.

This was back in 2005 and none of the carts had milk. Only some of the counter service places did - so many of them did not. We went back in 2009 and I noticed more CS places have milk but there are still lots that do not. She would not drink juice so it was water or nothing.
5. We waited until she was older to go back to WDW. A super long wait for me, but our experience was night and day! We went this past summer, June 2009 and she was 6. She had a fantastic time! She really enjoyed it tremendously and so did we. It was lots of fun experiencing WDW with the kids (she at 6 and my DS at 13).
Anyway, I know when we went in 2005, I knew it would be an exhausting experience at times and it was.
Personally, we would have waited until she was older around 4 for her first trip but my DS is seven years older than her and we did not want to wait any longer to take him to Disney for his first time. He was 8 at the time.
We tried to stay together as a family for most of the time since it was our first family trip. In hindsight, it would have been better for us to split up more (DS and DH and DD and I or DD and DH and DS and I). We split up some and those times helped. My DH and I took turns staying back at the resort with my DD.