I don't own one, but someone that I know recently got it, and he loves it. It actually did remind me of the Gameboy Advance, just the way it felt in my hands. It's pretty close to having a tablet-like feel, since it's much taller than the GBA, and it was surprisingly comfortable to hold. I wouldn't buy it over an actual 3DS, just because I'm a huge fan of the 3D effects that a lot of games take full advantage of, and I do like the design of the more traditional DS family. It's a perfect alternative to someone who's more casual though. My friend just wanted to get back into the Pokemon series, and because he wasn't very interested in any other games or just the 3D effects in general, it was an easy choice.
I did get the opportunity to get that awesome Zelda 3DS with Ocarina 3D, so I won't be getting one.