No, the N3DS isn't an improvement: it's a DLC'd version of the 3DS that should have been released first.
The N3DS does way less than what the DSi and what the GBC did to their predecessors respectively.
Sadly, the problem is that Nintendo often does the trick of "We swear that there won't be another model" before fooling people out with another "wannabe improved" model.
Plus, sorry, but, aside from games made with the N3DS SDK, the basic CTR games (old3DS as people say) can't take advantage of most of the gimmicks the N3DS gives, aside from the "converted" ZL/ZR bumpers, and the doorknob thingy called a C-Stick.
Hence why I don't get why people get amazed by the N3DS, when an "old" one performs as better as the "new" one on, let's admit it, 98.99% of the games. And don't get me started on how terrible the N3DS-only library is, as it is only made of smoke screen games, that doesn't even deserved such a poor portage (XC3D is murdering violently XC with an hundred stabs of aliasing and FPS drops, while Binding of Isaac 3D... Why such a good game is even used as a smoke screen anyway? Do it on PC!).
So, no, I'm not trying to be an anti-N3DS guy seeking to start a flame war, but, I don't get why the usual cycle of Nintendo's handheld trolling always work more than perfectly with people going surprised over terrible arguments. Okay, it's Nintendo, and they do have some solid arguments, but... they aren't that solid to anybody who bought the last model and who feel betrayed.