5 Reasons given at Wired although they're probably buying anyways...

ven amid insistence that the system has a place alongside the DS Lite on American retail shelves, at least for the foreseeable future, I’ll wager that many, like me, can’t help but wonder if this device will prove to be the new face of mobile gaming. And, if so, wouldn’t it be prudent to get onboard early?

Well, I guess that depends on how these new features stack up. Let’s take a look, shall we?

 

How about the camera? The most highly touted modification to the DSi is the inclusion of two – count ‘em: two – digital cameras. In addition to the one visible on the exterior of the unit, the DSi also boasts a second camera on the inside of the system continually pointed at the player.

All things considered, the DSi seems to be a mixed bag. It certainly adds some functionality, but much of it appears mediocre at best.

....

So now, after this lengthy diatribe about how the DSi may well not be worth the $180+ they’ll be asking for it on American shores, I will admit to you that I’ll probably buy one anyway. 

http://blog.wired.com/geekdad/2008/10/5-reasons-not-t.html