Just got back from Target. They didn't have it at Best Buy, so I drove around till I found a display. My first thoughts... I'm amazed. Though it's not the kind of 3D that pops out right in your face, it's something you have to see to believe. Like what Bright Neko said, it's like looking into a window. There are some things I didn't like about it though. It's not a major issue or anything, but it's with the idea of the gyroscope. If you were to move around a lot, you'll lose the eye magic, but it really depends on who's playing. If you were in my shoes I was holding the 3DS very still and I enjoyed every minute of it. I could see it a minor problem, but if you hold the system still, then there shouldn't be any problem.
I was kind of disappointed that they didn't have any other games set up like Street Fighter IV 3D. They only had Pilotwings Resort. I was kind of upset, but after playing a bit of it on Free Flight, I really enjoyed it. I had a blast until a family told me to get out of they way and let their kids play. I was on for about 30 minutes when I checked my cell phone for the time...
All in all the 3D was pretty good, but it's really easy to lose that sweet spot when you're moving the system around. Just hold the 3DS still and you're good to go.