The Nintendo 3DS is here, we have a stack of games to play, and you can expect our huge, blowout review before the system's official release on March 27. I've been living with the thing, playing through the launch software, and trying to figure out just how bad the battery life really is. Spoiler: it's pretty bad.

In the meantime, readers have been asking about the 3D effect—are we getting tired of the sense of depth and turning it off altogether, as others have already reported? The issue isn't that cut-and-dried, as each game seems to have its own 3D sweet spot. Some games are fine with the 3D slider put to maximum, while others don't seem to work well at all with any level of 3D. This is the smartest thing that Nintendo has done with the hardware: allow the players to adjust the 3D on the fly.

The switch is life

The 3DS' main gimmick is the glasses-free 3D screen, but Nintendo included a slider on the right-hand side of the device that allows you to adjust the 3D effect up and down or turn it off entirely. You don't have to go to a menu, you don't have to reboot the software, you can adjust the 3D whenever you'd like—even just to let someone watch over your shoulder—and it works beautifully.

If adjusting the 3D required you to leave the game, or even if it was simply a part of a menu, it wouldn't be nearly as compelling a feature. I can turn the 3D off before handing the system to my son, or bring the level all the way up for a single cut-scene. It's convenient, and this is important because there's no one-size-fits-all setting for the games.

Steel Diver looks great with the 3D slider all the way up. It doesn't add a ton of depth, but it does give more weight to the feeling that you're underwater, and some of the little details in the game—the schools of fish and the rainbows above the water's surface—really pop in 3D. My eyes never felt strained or sore, and the 3D effect looked weak when dialed down.

In Madden I was unable to keep the 3D on at all. There are too many details and bits of information to take in between plays, and having my eyes constantly adjust to the 3D field and then the 2D text was incredibly hard, to the point where my head began to ache after only a few minutes. Turn the 3D off, and the problem goes away. When you're playing games on the 3DS, you become acutely aware of what your eyes focus on, and smart developers are going to have to pay close attention to how their menus are laid out.

Pilotwings Resort is a game that wasn't as easy to nail down. With the 3D maximized, it was hard to switch focus between my vehicle and the environment, but it sure did look cool. If the 3D was turned all the down I am actually at a disadvantage, since the ability to perceive depth offers some clues about where I am in relation to other objects in the game world. Twitchy things like landing with the rocket belt become much easier.

For my money, the sweet spot with the 3D slider is about 30 percent of full power. Enough to get a sense of depth, but not so strong that your head hurts. There is one mission with the squirrel suit—which feels like a more controlled way to skydive— and for that incredibly fun portion of the game I turned the 3D slider all the way up, and felt dizzy in the best way.

It's a constant adjustment

People who have strong opinions about the 3DS may find that the reality of the hardware is much more nuanced, as the games all use 3D effects in different ways and require a different setting for comfortable play. Sometimes I would turn it off just to give my eyes a rest, or turn it up to take in a pretty piece of scenery. The option is always there, just a flick away.

The 3DS would not be nearly as effective or fun to play if that little slider were taken away or obscured in some way. In a system that does as many things wrong as it does right, the real-time 3D adjustment has quickly become the hardware's most-used feature.