No problem here. Last Sunday I put in about eight hours of play, all in 3D. 3D slider was set at around the half way mark. I did find myself trying to focus through internet pages afterwards though, like trying to bring text or pictures out of the screen.
I heard that the people that are feeling dizzy are people who have got un-diagnosed visual problems and may need glasses. So if you start feeling dizzy whilst playing the 3DS then go get your eyes checked, as it is most likely to do with your eyes, not the console.
I got a little dizzy when I first started playing the 3ds the day I got it when I turned on the 3d part for maybe 2 minutes top's. I bought my 3ds mainly for the new 3ds & ds games the 3d part doesn't hold my interest at all but still wanted to try out the 3d part for a few minutes after I got my 3ds on launch day I haven't used the 3d part since launch day but love playing nintendo dogs + cats: french bulldog 3ds game. I just alway's keep the 3d part turned off & play it like a regular ds system like I said bought it for new games plus also the virtual console part in the e-shop when may comes around next month.
Only when I first got the 3DS and "hadn't adjusted it correctly", I can now play on it fine with no problems at all. although if I am tired I may get eye strain.. The "Sun" reports make me laugh, "people are denied a refund as games make them feel sick" urm.. buy a PS3 game from HMV or something, then try returning it saying it makes you feel sick.. they will only offer a trade in.. thats it, thats all anywhere will offer these days due to "piracy concerns", unless there is something faulty with the game that you can prove, they won't ever refund it.
And for those that do get the problems.. the 3DS has a LOT MORE going for it then the 3D-nes, yes that is the big selling point, but it still has better connectivity, better graphics and a better control system, turn off the 3D and enjoy the console otherwise.
I have astigmatysm but i can see 3d at the cinema fine so assumed i would be ok with this. Within 3-10 mins of play I felt like i was going cross eyed. My left eye was really straining and it was pretty uncomfortable. I also felt a bit dizzy and it took a further 10 mins before i could focus properly as i started googling to see if anyone else had the issue. In the end the only level that worked was to have the slider on 2d