A bit late, but I thought I would chime in anyway.
There are 5 Pervasive Developmental Disorders:
Childhood Disintegrative Disorder (CDD)
Rett's Disorder (RD)
Autistic Disorder (AD)
Pervasive Developmental Disorder - Not Otherwise Specified (PDD-NOS)
Asperger's Syndrome (AS)
There are still alot of Dr's out there that do not understand the range of the PDD spectrum and will often give a diagnosis of any number of the above mentioned.
PDD-NOS is when the individuals do not meet all of the requirements of the strict criteria for autistic disorder.
PDD is actually the correct diagnosis for anyone that falls within the spectrum (any one of the 5 Disorders) and because it is often difficult to detect some of the "symptoms" of children under a certain age (usually into their 2nd or 3rd school year) they don't get a more specific diagnosis until then. It is true of some adults as well~if they have lived life without a diagnosis and adapted to the world around them/receiving accommodations or modified daily living, it is also difficult to give a more specific diagnosis than the broad range PDD covers.
If interested in reading more~here is a link:
Understanding Autism Spectrum Disorders
As for accommodations or things to consider, it really is all individual.
I have 2 children that have 2 completely different set of needs, but are on the same spectrum.
One is sensory seeking, the other is sensory defensive. One has high anxiety, the other fears NOTHING. One has MAJOR motor control problems, the other has absolutely no fine or gross motor issues.One (3 years old) likes fast paced, rollercoasters/rides and the other (nearly 12) needs to be coerced into just about EVERYTHING and boycotts rides.
Both have no love for loud, unexpected noises and often cover their ears with the vacuum, trains, fireworks, etc. and are EXTREMELY "picky" eaters with oral motor issues.
We do not take alot of breaks at Disney because it happens to be the biggest "special interest" (another PDD trait) in our home. They'd both be happy to go from morning until midnight, but we know (and have met up) with other Disney addicts (on this thread) who quite like/need their scheduled breaks in the day.
Our youngest is "a runner". She fears nothing, has little understanding of boundaries and has no sense of danger. This is a huge safety concern for us. The last couple of times we have been we explained the need for the stroller and requested a "wheelchair" sticker because of our safety concerns (another lovely tip I learned from our fellow DISer

).
TBH, the GAC has more than tripled our experiences at Disney and is probably one of the biggest reasons Disney *wins* each and every time.
Difficult to find such amazing service and the accommodations come without the stigma. We never feel out of place or like we are inconveniencing anyone because of our needs. In fact, we always feel like we are VERY well taken care of.
Hope this helps.
MLH