If you want the worst attraction, it may be Superstar Limo.
Cars Land is the new Potter... a lot of frustrated guests a long wait times until the excitement wears off a bit.
Search results: http://www.youtube.com/watch?v=rDNT-UmvuLA
John Lasseter seemed to be moving pretty quickly on his test run, as you can see from the video.
The single biggest issue in my opinion is the separate loading-unloading area for disabled. It is very problematic since it requires them to restart the ride and then direct the tire into this special area. This takes a considerable amount of time. I would not have included this if it were my attraction and if it were required I would've killed the entire project.
I love the separate load-unload areas on tracked rides. It works great and results in no inconvenience for the rest of the riding folks. In this case it is a disaster.
Anyone going to Cars Land right now and expecting anything less than long lines and big crowds is obviously living in false sense of reality.