Guys..
I havent bought one of these units yet (in real turmoil.. should I/shouldnt I)
but I am feeling your pain with regards to boot time..
to reduce some of you pain..
here is a link to a very simple delayed turn off circuit.
http://www.astron.nl/~smirnov/poweroff.html
This will provide about a 10m delay before cutting the power for good.. and it also has an over ride button to kill the power instantly if you know you wont be returning to your car in 10mins
Amit