I agree -- take them early!! It certainly helps if you have DVC, though.
We took our first daughter at 3 months old...this trip was for DH and I celebrating our new baby at the POLYNESIAN!!!

But it was actually sooooo easy to do ... just slap her in the Bjorn or the stroller and away we went...stop to nurse on a ride (TTA) or show or at the Baby Care center and away we went. Then we took her at 26 mo and 33 months.
Now we're taking our 2nd child at 8.5 months in November and again when she will be 16 months old in July.
What's really cool is to see how your child 'grows at Disney'...which rides they are scared of and which ones they enjoy. Also, I have some great "family tradition" photos and we'll continue to take a pic at the same spots year after year.