I've been observing this from a year ago in my test drives then... the main screen is very well laid out, very quick and easy to navigate, very intuitive... except for the "Controls" section.
In the Controls section, there are way too many layers, side menus, top menus, half screens, etc. making it slower to find/remember how you get to certain functions.
TM needs to break a couple of these out, and add perhaps a button in the main nav for this...
Need to break out the "Settings" and "Charging" sections from Controls, this might help improve simplicity of the controls section, eliminating the need for the horizontal nav in this section. Leave the charging access to the battery icon at there very top. I would then add/create a settings icon to the very top nav row, and use the ubiquitous "gears" icon for this section.
Also the look and feel for the very top row of controls/icons is far too "cell phone" in feeling to me. Why do we need to follow this UI set? Can't we improve on these icons, and make them a touch bigger while we're at it?
It's better to improve on this UI now, before there's too much (User) legacy out there. Get it right before the Model X comes. Set some new automotive glass cockpit standards for UI.
Also consider how Apple is now moving away from the pseudo cartoonish UI, to have the software look and feel worthy of the hardware it resides in... to be more harmonious/holistic.