I finally did my test drive today and am reservation holder #11640.
First of all, my current car is a fully loaded 2006 Toyota Prius with everything except leather. I test drove a standard Model S with the 60KW battery with the tech package and active air suspension installed. It did not have the pano-roof installed.
I found the performance to be quite good. While I wasn't able to push it hard while cornering during the test drive, I noticed that there was no body roll and the steering felt quick and precise. In some ways I prefer the standard steering over sport mode but I didn't have enough time to fully experience it. I need to take it on a road like highway 9 to really test that out. Road noise wasn't bad, especially considering how bad Bay Area roads are. It also had plenty of acceleration, far more than I'm used to (considering I drive a Prius). I was considering the performance model before but now I'm not so sure. I was doing 80 before I realized it :). Acceleration felt effortless and perfectly smooth and instantaneous. That's something else I'll have to get used to. I'm used to the 1-2 seconds of lag with my Prius.
The interior was spacious with plenty of head room and the seating was quite comfortable, more so than my Prius.
I noticed that the left mirror did not aim as far to the left as I would prefer but it was useable. My rule of thumb is to move my head to the left side and aim the mirror until I can just see the left side of my car. While driving I quickly noticed one thing I will definitely miss from my Prius. My Prius has a lot of buttons on the steering wheel so that I never have to take my eyes off of the road in order to adjust the radio or climate control, including things like defrost and recirculate. There are dedicated buttons for changing tracks/stations, mode (CD/satellite/FM) and volume for the radio and just about everything for the climate control. The controls on the Model S are flexible, but may require taking your eyes off of the road to change modes. I often use many of the climate control buttons, like pressing recirculate when driving 880 through Milpitas (due to the stink) during my daily commute as well as using the defrost controls. It also allows me to easily switch my view on the touch screen, though this isn't so much of a problem with the huge touchscreen on the model S. As utilitarian as my Prius is compared to the Tesla, I think the ergonomics may be a bit better since there is less reason to need to look at the touch screen since most of the controls I need during driving have dedicated buttons which I can control by feel.
I think I will also miss the center console storage I have in my Prius and the spot reserved for placing sunglasses above the rear-view mirror. My Prius also has a second power plug inside the console as well as an AUX audio port (not sure if the Tesla has an AUX port). The AUX port isn't really needed with bluetooth though.
One feature I would really like to see is parking sensors. The Tesla rep I spoke with (who is also an owner of a Signature) agreed since he admitted to already having a couple dings added that would be avoided had the car had this feature. While I don't require this for backing up, it is helpful on the side and front to keep from scuffing the rims or front of the car (as I have done repeatedly with my Prius). Also, lines in the backup camera would also be helpful as people have reported in other threads. I'm also surprised that some other features found on less expensive cars are missing such as adaptive cruise control.
I do like the dash LCD display. It is quite clear and easy to read at a glance. My father has a Fisker Karma and I feel the Tesla dash is much easier to read. The touch screen in the Tesla is also much better in my opinion. It was quite responsive (unlike my Prius).
I did not get a chance to test out the sound system. I don't think they'd appreciate that in the show room even though I have music on a USB thumb drive (.flac) for just that purpose.
I need to make a decision on how I'll configure my car by January 10th. I have even more to consider after my test drive than before, such as do I save $12K by not going with the performance model?