My interest in the 3DS is mostly based on its games, so I don't plan on using the 3D unless it's actually beneficial to gameplay. I think Nintendo made a mistake when they decided to incorporate the 3D as heavily into the system's pitch. Many folks see it as the only selling point, or think that's it's just a regular DS with 3D.
I'll wait for the next generation, though, since the battery life on the 3DS right now is really sub-par
From what I hear it's not too bad if you don't use the 3D or have the brightness too high, but it's still pretty close to Nintendo's figures (~8 hours). Nyko already has a http://nyko.com/products/product-detail/?name=Power+Pak%2B in the works, which is said to double the system's battery life, but it's a bit bulky so I'll wait to see what other companies come up with. Not that I really play my handhelds on the go, but it'd be nice to be able to take it on a trip or something.