With the original DS, you could turn on the auto start-up mode and the console would load the game cartridge without going through the menu. As I install new games/apps, the menu of my 3DS is getting slower, so I keep pressing 'A' impatiently for some valuable seconds until the game starts loading.
Is there a similar configuration for the 3DS? I have seen a post claming that Nintendo wants you to have your 3DS always on, but I like turning off my 3DS completely instead of using the sleep mode - I couldn't care less about street pass and such.