This device was a huge hit at E3, possibly the most talked about at the show. I find it interesting that there were many naysayers regarding 3D in general (calling the actual 3D itself a useless gimmick and fad that will go away in a few years), and yet, there was a great deal of frenzied excitement for this 3DS at E3. (3 hour long lines just to play it). Despite it being on a much smaller screen and at a much lower resolution than any high end BD or RealD movie experience, it was still popular. So I guess the public is actually very interested in 3D, but have found the glasses to be the barrier? Never knew that many folks were so fashion-conscious.
I think one of the Gizmodo editors said that you do have to keep your head rather steady, sort of keeping it in an imaginary bubble. Any time you move out of the "bubble" the 3D effect is lost. But when it works, it looks surprisingly good. James Cameron said that autostereoscopic 3D laptops will be arriving in a few years. I think with the devices like 3DS hitting the mainstream, there will be a push for more of this type of 3D in laptops and cellphones. In 5 years, a 2D cellphone without a touchscreen will look ancient (which will probably describe mine).