I had my DS in late August, 2002, and his first trip to Disney was 6 weeks later in early October. We had a great time. I will admit that we only considered the trip because my DH had a conference there and we felt that our DD's (6 & 8 at the time) deserved a fun trip after being home all summer with a mommy in her 3rd trimester of pregnancy. It wasn't our most fun summer.
While there, we ran into friends of my DH's who were there with their 3 yr old and 7 week old DS. We both talked about how nervous we were to take the trip, but how happy we were since we were having such a great time. We both really needed some family fun.
I will admit that it depends on the baby. We were lucky that our DS was our best baby (although that has changed since he has become a toddler). Since I had a c-section, I would go back to the room often with DS when I needed to rest, while my husband took the girls swimming or just remained longer at the parks.
Goodluck with your decision. It definitely worked out great for us. By the way, I had the blessing of my pediatrician as long as I kept him out of the sun. While it was still hot in Florida, he never seemed uncomfortable and actually slept better from being outdoors so much.