I bought the DS when it was released, the touch screen had a dead pixel. I exchanged it. 4 days ago the reception on my touch screen became distorted. The visuals are very faint, comperable to someone jacking up the brightness on a standard TV. Nintendo is sending me a replacement.
I'm playing "Feel the Magic" last night with head phones at a low volume. There's a lot of static interference. This can be fixed with a game like Mario 64 DS that has different sound options, but it's just a bit disturbing that this is considered normal performance. This feels like a rush job for Nintendo. The system is difficult to hold when using the touch screen with the left hand and the buttons with the right. I've turned off the system when using the stylus due to the fact that the power button being at the same level as the control pad (they did do a nice job in it's detection of accidental presses--quite a few times I thought it was a start button and pressed it. I like that you have to hold it down). There's no control on the system to turn off the backlight like on the SP. Only DS games that support it in software can do it. If I'm playing a GBA game that doesn't support sleep mode my DS just stays on if I need to take a break.
To top it off, I think everyone is making too big a deal about control issues in Mario 64 DS--I don't think he's that difficult to control with the touch screen (other than the afore mentioned difficulty in posturing the system). As soon as Nintendo makes a new version of the DS I'm going to buy it, because I like the idea, but I'm just a little dissapointed with the hardware right now.