Proably not a lot from Apple, but a TON of stuff from Unix.
Any Linux user today can tell you that the world famous "Aero Glass" feature on Vista has been available on Linux for at least two years, It's called Ruby and Beryl. In fact, it's way cooler than Aero, which makes you be able to see through an opened window a little bit, especially at the title bar area. (whoopety doo!) With Ruby and Beryl you can not only see through it, you can grab a window and shake it with the mouse and it jiggles like Jello. When you minimize it, it kind of wiggles, wraps up, then zips down to the taskbar.
Also, where in Vista you can point at a minimized program on the taskbar and it shows a little preview of what the page is, Linux has been able to do that for years.
Security wise, you can encrypt all your files in Vista or XP and then browse to it from a computer with Linux installed and there's all the files, bare naked in all their glory!
Last but not least whereas Vista Ultimate is $400. XP still hovering around $100, any version of Linux is absolutely free, in two ways, it doesn't cost anything, and you're free to modify or change or sell the programs any way you see fit. (I use Ubuntu)