That's quite ridiculous; iOS style multitasking is severely crippled.
XNU does multitasking fine already; there's no need to screw it up. If you're sick of Safari's memory and CPU usage, just switch to a different browser, but to say something as absurd as wanting task-switching on a desktop OS just for the sake of CPU cycles is short-sighted and a prime reason for the fall of productivity and change for the sake of change.
iOS style multitasking is great for battery life. And for the foreseeable future: 1) I'm not going back, voluntarily, to being tethered to a wall socket; 2) Lithium-ion batteries aren't getting more capacious very quickly.
How is it great for battery life? When applications are inactive, they're already not using CPU cycles. Task-switching involves focusing context, which does eat up CPU time, whereas with standard UNIX multitasking, switching between tasks doesn't switch context.
You could remove the context switch from the equation, but then you'd end up with a setup similar to the current multitasking system, so it's all for nought.
I'm not suggesting that we rip out the existing multitasking ability in OS X. Just the option to freeze SOME apps when I switch away from them, and unfreeze them when I switch back. I can already do this with "killall -STOP Safari" and "killall -CONT Safari". The only thing Apple needs to do is to make it automatic.
XNU does multitasking fine already; there's no need to screw it up. If you're sick of Safari's memory and CPU usage, just switch to a different browser, but to say something as absurd as wanting task-switching on a desktop OS just for the sake of CPU cycles is short-sighted and a prime reason for the fall of productivity and change for the sake of change.