The original DS and DSlite had a rumble pack, but very few games actually used it. It looks like Nintendo isn’t completely abandoning the idea of having rumble in a portable though. A patent filed late last year shows that they might have plans for a way to add tactile feedback to games utilizing the touch screen.
“A game apparatus includes an LCD, and a touch panel is placed on a top surface of the LCD. A player instructs an enemy character displayed on the LCD by use of a stick to attack the enemy character. For example, in a case that the enemy character exists at a depth of a game screen, little damage is applied to the enemy character, and a weak vibration is applied to the game apparatus. Conversely, in a case that the enemy character exists at a front of the game screen, much damage is applied to the character, and a strong vibration is applied to the game apparatus. In either case, the vibrations are transmitted to the fingers or hands of the payer via the stick.”
The only problem I could see is with quick taps you probably wouldn’t be able to feel the rumble much, but for dragging objects or say moving a character it might perform well.
Again though, it is a patent so this may or may not see the light of day.