And I am very glad that you actually have looked around a bit. You have restored my faith in newbies. Seems to be an onslaught of dummies recently.
But welcome! And of course, Honda ftw!
For 2 & 3, see below...
If you are still reading and not bubbling with anger like most Mac fanboys, I will tell you why.
Since the Intel switch, macs have actually become useful again. Their hardware is awesome although expensive. But their os is lacking in all regards when it comes to car environment.
With the mac or with linux for that matter, you have a very very limited number of choices for your software. If you were to run <gasp> Windows </gasp> you could run a frontend such as RoadRunner, or Streetdeck, and Navigation such as iGuidance, or Streets & Trips. Also XM and Sirius is Supported.
Want to know the best part? You see Windows for a split second as the desktop flashes and bam, you are in your frontend. And if you dont even want to see that, then you can boot your frontend as a shell, and then it would be completely unnoticeable what OS you were using except you will actually have functionality with your CarPC, not like 2 apps that actually work.
And despite what a lot of people think, M$ is no longer a buggy piece of crap. Everything after 3.0 all the way up to ME was just a complete disaster. XP was better because it basically shoved all the bugs in the back, meaning no more blue screens of death.
To give a real world example: GoHybrid has had his mac installed for a while and I think he said 1 freeze/restart. I have had mine in for over a year now, and I have had 2. Both restarts. Within 25seconds, it was back up and playing music again. I still think it was faulty RAM because since my switch to a new stick of RAM, no problems.
So, to sum up, just stick with what is supported, and if you want then make it look like OSX and just tell everyone it is.
If you want good GPS programmes, Good satellite radio, good FM radio, good 800x480 resolution (important to some), Great Front ends, and pretty much anything else, stick to what is supported because you will (except for configuration which isnt that bad) you will never even see the stupid multicoloured window.