I just bought my son a 3DS for his birthday. Judging by his squeals of joy he's enjoying it immensely!
He had his DS: Lite for over 4 years and played it daily. The new Super Mario 3D
game is going down a treat too, as is the Lego: Pirates of the Caribbean
game, so I'm happy. As for the 3D, he only has it on while playing the games that support it, but he's actually more interested in using the other functions of the 3DS (the 3D camera and camcorder especially) and he's getting into short moviemaking because of it. Cool as far as I'm concerned.
I myself am not a huge mobile gamer, so that effectively brings to a close any need of mine to get another portable system. We still have the original DS:Lite in full working order after all.
Note: This isn't about which device is better, but which is more suitable
Freestyler: A customer that's too hard to please, complains all the time and wants everything for next to nothing.