Wow, where should i start,,
How about beryl/eyecandy. Whoever said that this is unimportant couldn't be further from the truth. Yea, some will say that it increases productivity (and I agree 100%) but, your missing the big picture. "Eyecandy" is exactly what most home users want. If Linux wants to compete with Vista or OSX on the desktop it has to have beryl/compiz. Beryl with convert more home users to linux than almost any other single app.
MacBook for security Testing- if you're talking abt just the hardware, as long as you're using Intel based proc. you'll be fine. If you're talking abt software/os you're going to want linux.
As for using Ubuntu, this is probably the worst distro for security.
With ubuntu, you don't have access to the root account which is what you need to run most main stream security software (i.e. nessusd)
If I was you, I'd buy a cheap used laptop off ebay and load fedora/gentoo/slackware on it.
</end rant>