Is optimus tech also going to go into desktop systems? A core i3-based mobo that could completely shut off the graphics card when not needed would be nice for htpc, for example.

The point of the demo is NOT that it can be removed.
It's that the module is FULLY powered down.

This demo is about power efficiency and driver capability. Pulling the module out is just a "proof".

Yes cool! But still this has no practical use. How about pulling out PSU while still running?

Practically that is dangerous, not to the GPU but to other parts of the system. We know that even touching some wires there while running makes the computer unstable how much more we pull some cards there. Unless your mobo is fully bolted hard but still it bents a little by pushing and this will cause some tiny short circuit or may loosen other parts.

Great battery life is not due to ION inside it, but the Intel's GMA inside it, even without ION, it has still great battery life, in fact reduced by adding ION on it. Nvidia is wrong on this stunt, they should not claim it.

For whatever stunt this is, DirectX 11 is much cooler than this. So where is that card anyway?

It is cool. And of course it's useless by any kind of practical standard. But read the last couple of lines again. If you can walk into a meeting with your customers and make their tech guys' jaws drop open, you just grabbed a lot of mindshare amongst the people who actually decide whether your tech gets designed into products that sell in the millions. That's anything but useless.

Of course nVidia isn't exactly a start-up looking to grab ODM mind-share; they're going to get considered regardless, and factors like price ultimately matter more. But things like this still have an impact.

What a waste of time and effort.
But it should boost GPU sales when users misplace or damage the interchangable component.

I think the key here is "That's because the system completely powers down the GPU module (and the associated PCI Express interface) when it's not needed". So... what happens if you're using the discrete GPU when you pull it out? I think this is especially relevant because this tech relies on drivers to recognize certain 3d-intensive apps, so it doesnt' require the user deliberately to switch to discrete graphics.

Call me old fashioned but I would unplug and pull the battery. It's a good demonstration of the power saving features of Optimus though which is the obvious point.

cool but useless

Cool I suppose, but I still it in the category of useless gimmick.

Well, now when your old laptop isn't quite up to snuff for that new game you're running, you can just upgrade it - without even stopping the game...