Rode it yesterday about 4 times. Not every effect is working yet, Today may have been the first day with everything on...
Spoilers ahead!
The actual ride is actually referred to as the Sim Track.
Heavy use of Blacklight and brings a sort of Tron Vibe. Almost all traces of 98 Test Track are gone! (Exception of some Black and Yellow paints in Load/Unload areas and the Maintenance Bay) And the Semi-Truck gag is back but really well done.
Lots of little references to EPCOT Center, World of Motion and even a Cars reference!
Designing the car is very similar to Sum of All Thrills! But a lot more fun! you can create anything from realistic concept car to Even a huge Truck that looks like a tank! (Thats what I did!)
Did not experience post show beyond the big screen that shows every ones car and stats (Much like the Globe post show at Spaceship Earth)
They were cycling cars much closer than what I remember... On the Speed Loop, I felt like a Hot Wheels on those old plastic dueling tracks with the motors.
The design stage has variable design times of 9 mins, 7 mins, and 5 mins. Based on line length... So I see it never going to 9 mins, maybe 7 mins in January/February.
The line will constantly have at least a 60 min wait time. Fastpasses will be gone in an hour. Because every family with a male child will want to go and design their own car. Actually everyone will want to ride, even if all they want to do is design their own car.
My opinion: Even with not everything working right quite yet, It is a significant improvement over the past Test Track. No more industrial feel, all sleek Tron/Epcot Center feel. This is the best re-imagining Disney has done at Epcot,or even Walt Disney World, rivaling Summer Nighttastic's Tower of Terror. Its a must not miss.
But I will say this: Bill McKim. You will be missed...