After I got my DS I upgraded to a DSi. Now I've gotta upgrade again?
The 3DS is a different system entirely (even though it still contains DS in the title), the DSi is an upgrade from the DS.
From a personal opinion and perspective, the DSi is a cheap knockoff that was only made to "print money".
They add a camera and a little shop channel for bogus apps, and take away the ability to play <GBA games. Then they make it into an XL for those who want to stretch their pixels.
I never "upgraded" to DSi's as I have always found them to a poor excuse of a console "upgrade". The DSLite was the only "upgrade" that was at all decent.