Pros: Almost everything, as for eye strain (I could take 8 hours of 3D just fine which is average time for gamers)
Cons: Power button is in a very precarious place (at least it will show options to go to the home menu and shut down when it's pushed during gameplay instead of turning it off), you are prone to push it instead of start which you want to push. I had this happen twice.
Losing the 3D effect is a common occurrence especially if playing the 3DS lying down both back and chest down and can be an annoyance at times.
3D effect isn't as good in a well lit area, so turn off those lights