After riding a few more times, unfortunately I am a bit less optimistic about the makeover as I was initially. I predict that everything about the designing aspect is not going to go over well with the average guest, and may ultimately need some re-tooling. Before you bring up the unchanged SSE 2007 descent and it's negative reaction from fans, keep in mind that for SSE, the average rider isn't thinking about the ride being anti-climatic, having a drastic change in tone, etc. Rather, they are getting a kick out of seeing their head on a cartoon body looking stupid.
Maybe it will improve with time, but waiting to enter the design studios (there are two with either 16 or 20 design kiosks each, not sure which number is right) is a sluggish process. The rooms are essentially pre-shows, but the cycle time is a bit longer than the typical pre-show. Designing your car is fun, but is a hand-held process like Sum of All Thrills, which is to be expected. For example, you draw the outline of the shape you want your car to be, but it then makes you click "Optimize" - in which its actually selecting the pre-set model that most closely resembles the shape you drew. From there, you select and tweak other pre-set options, though admittedly there are a lot more than you would expect.
From here, you (as in, a first time rider who knows nothing about what to expect) are left with the assumption that your creation will have a meaningful impact on your ride experience. I guess the biggest problem I have with it, and keep in mind I already knew the circumstances, is just how little it ends up actually mattering. Basically you have the four categories of testing, and after each of those segments on the track, a screen displays the cars that have been uploaded to your SIM car and ranks them in that category. That's it. There isn't really even too much of an element of surprise in the rankings either, since you already know how your car performs in those categories during the design process.
I can see the average guest either not even understanding the purpose of designing your car and uploading it to the sim-car (in which case, the ride will make no sense to them), or, if they do "get it", being completely disappointed in the fact that it doesn't change anything other than what's on the ranking screens.
Now, I don't exactly care for interactive elements on rides, whether real (TSMM) or faked (Mission: Space), so on one hand I'm relieved that the actual ride isn't truly interactive. But, on the other hand, since they bothered to do it... I guess I feel like the payoff of having to take the time to design your car should have been better. Also, the entire onboard narration is basically trying to convince you that your design does matter.
Now, on to the ride itself... At first, it was simply exciting to see the familiar Test Track "track" with completely new window dressing. A lot of that excitement comes from comparing what it looked like before to now. Now that that newness has worn off for me, I feel the visuals are just a bit lacking. One thing I'd like to point out is that the ride looks amazing in the POV videos because they are darker than the track actually is. In reality, you can still clearly see the walls and, while it does still look very pretty and nice, it is not as convincing as the POV videos show. Stuff like the laser grid trees springing up and the new laser grid truck are very cool... but there could have been more of that. The three environment chambers are definitely the weakest part. The first room is either supposed to, or needs to, have fog in it so you can actually see the laser beams scanning your vehicle. The second room needs actual strong wind blowing at the car to match the visuals in the mirror. The third room doesn't even interact with your car in any way. And then there's of course the outside loop, which is unchanged and lacking any onboard audio.
In the end, I still feel that this is an improvement, fits Test Track appropriately in with Future World, and gave it the face-lit it definitely needed. I just think it may not be the grand slam makeover we all initially thought it was.