3DS is not worthwhile yet, at least for now.
It's still an expensive cheap plastic handheld, not too different from the DS. The 3D is not that amazing and most people are turning it off after one one week of use.
The initial games lineup is very weak, all of those could be simple DS games.
To make things worse, DS game compatibility is bad, so forget about selling your DS to help buy a 3DS and keep playing your DS games.
The only saving feature is that it's a little bit more powerful than the DS, so I guess that soon or later a few good games will appear. DS has nice games (among a ton of shovelware), so I have no reason to not believe that will be the case of 3DS.
A pitty it doesn't have a second analog stick. A big missing feature in the PSP, corrected on PSP2. I guess Nintendo didn't care yet. Maybe it wil with the 3DS Lite.
Right now, it's foolishness to buy a 3DS. I'll wait until:
- the price drops a little bit
- good games are released
- a Lite (or similar) version appear
- flashcards are made available.