1 - There are heaters in the side mirrors that that switch activates for a few minutes, it will also activate the defroster on the optional hardtop and optional glass soft top upgrade.
2 - Don't leave it in gear at stop lights.
3 - No, get used to it. Give it a few weeks and you won't even notice. (Unless you are switching between cars a lot)
Congrats on the car, but like others said be prepared to spend some cash. It may have cost the same as an Aveo but it doesn't cost the same to keep running. For instance, yesterday I spent $350 on two new rear tires, thanks to a 10¢ nail in my sidewall. On a regular sedan I would spent around $200. (BTW it actually cost $500 since my alignment was off, plus tax.)
The Boxster is a great car, but they cost more than an Aveo to keep running (so brace yourself)!