So I bought the N3DS a couple of days ago. A portable gaming console from Nintendo with a 3D display that does not require glasses to see the 3D effect ! The reason I didn't post anything about it yet (expect a quick facebook mssg saying I grabbed one from the store during lunch) is I wanted to give it a thorough workover first.
The 3D effect works great. It's true 3D, but a little different then what you see in the cinema. Instead of things popping OUT of the screen, it's like your 3DS is 4-dimensional and the depth goes INTO the screen. I'm very impressed with the effect and so is practically everyone that has had a chance to play a bit with it.
I have ony 2 games for it at the moment, PilotWings Resort and Tom Clancys Ghost Recon. However, so far the most fun has been had with the built-in features for augmented reality. I could try and explain but a picture tells a thousand words, so here's an example :

Ewout and Mario at the office
Hopefully lots of cool games are going to be released soon, because at this time the availability of games is a little limited. My personal recommendations for 3DS games at the moment are : Anything but Nintedogs :) Seriously though, for the most impressive 3D effects I like to play Pilotwings Resort. It's also the only game at this time where the 3d effect really adds something to the gameplay. You have to fly through loops in the air and the 3D effect will actually help you see the distance etc to the hoop, making it easier to steer through them.
Headaches, barfing and going permanantly blind. These are risks I am willing to take to be able to use this exciting piece of kit. So far, no issues at all ... I think I would get a headache if I was playing it for hours on end and not holding it properly in front of me ... if you dont hold it exactly right, the 3d effect goes away and you see everything double and THAT can really mess with your head. I have not tried playing it in a moving vehicle but heard it's not comfortable and not recommended.