I ran the full in 2005 and Goofy in 2007. I am NOT a hard core runner but I am a lover of all things Disney. For me, the half marathon in 2007 was the best experience, followed closely by the full marathon in 2007. The entertainment and spectators on the course has improved, in my opinion.
I will admit, by Sunday around 7am I was pretty tired of seeing people use the trees/bushes as a potty. I did wait 15-20 min both race mornings for the port-o-potties. After that, I used the bathrooms in the parks (MK for the half and EPCOT for the full worked out perfectly for me).

Highlights: Running thru MK both days; running thru EPCOT at mile 12.5 for the half marathon; running thru MGM on Sunday; running thru Ticket & Transportation center both days but better crowd on Saturday; Mary Poppins and Bert outside GF on Sunday; Peter Pan and Wendy in MK on Sunday; Piglet in MGM on Sunday. I am just hitting the characters that particularly inspired me--I have a roll of 24 photos that we took w/ the characters--they were out in force. (ex: cinderella/prince charming, belle/beast and mickey/minnie on Saturday at MK)
-There was better cross walk protection this year for the full marathon.
-Volunteers, one word--AWESOME! thanks!

Lowlights: walking! There is so much walking!!! From where the buses dump you off in the parking lot at 4am, to having to walk to the buses after the races---and especially to the start of both of the races! I know, it is difficult to haul around such a large number of people but it was just endless!
-I do not like the sharpie mile markers. Bring back the Disney mile markers.
-I would like Disney music when running thru the parks.
-My husband experienced no water/gatorade at 2 of the water stations late in the full marathon. There is no excuse for that to happen--they had been predicting hot/humid temps all week.
-I would love to have more oranges out on the courses!
-There are novice runners that participate in this race that run/walk 4-5-6 across. This race is so crowded and it is just rude to the other participants to hog the road and make it difficult to pass. Also, just as rude, is walking in the middle of the street instead of all the way over to the right--or even over to the left, if necessary.
-I do not train on highways...therefore, the sloped angles of the on/off ramps really bothered my legs and in particular, my knees. The grassy off road terrain is flatter and easier to run on.
I did not come close to hitting all the highlights--we really had a blast this year. Again, we are not hard core runners and we went in with the goal of finishing both races while having fun-goal accomplished!