Hawk52: I think it's more of a hindrance then anything for the DS...
PhoenixWright: A hindrance? Two screens is great, so is the touch screen aspect. Check out The World Ends With You or Zoo Keeper (the Bejewled clone) or something, it obviously has its uses, and I don't see how it gets in the way when it doesn't.
I tend to game sitting up, which means to use the stylus I have to hold the DS in one hand and the other use the stylus on the screen. There's also the problem with games that want you to use the stylus to move or interact with the environment. The hand and stylus naturally cover up part of the action.
It just comes down to personal preference. I'd rather just use the D-pad and buttons then a touch screen.