Even though this question has been asked a million times, I'll still answer.
I'm going to buy one at launch, just like I did with the Phat and Lite versions of the DS. The 3DS has me very excited, and I want to play one as soon as possible. Nintendo has come a long way with certain improvements in their handhelds, like the screen brightness, resolution, etc. Therefore, the 3DS harware as we've seen it, looks to include all the upgrades the DS hardware has achieved, and then some. The only way to improve is to make it thinner, have bigger screens, and beef up anti-piracy should the older model become hacked.
If you're hoping for an exploit, or to allow hacking/flashcarts, or whatever, you're simpy better off owning a launch system anyways. Besides, who wants to sit back and listen/read everyone talking about how awesome the 3DS is, wishing you were sharing the experience?