One of our favorite features of the DS is the ease of putting the handheld into sleep mode. You just have to clamshell the portable when you're tired of playing, and voilá -- it goes to sleep.
Some people might not like this feature, though. It certainly makes an in-game jukebox less effective, for one. So, what are your thoughts on sleep mode? Do you put your handheld to sleep often, or do you prefer to just shut your game off completely? And, is clamshelling a good thing, or would you rather the DS stay on when you close it?