DeadEye on 23 April 2011
I use the 3D nearly all the time. I have never had a problem with it straining or tiring my eyes and can play for about 20-30 mins non-stop before need a short break. The effect is quite cool when it works well, has a 'wow' factor it but that depends entirely on the developer imo. For example, in Nintendogs Cats / Home Menu / Built-in Software, it works really well (all Nintendo programmed ofc) but in Ridge Racer I found it to be a bit rubbish. Still an amazing feature though. Even without it though the 3DS is amazing.
