I got to run in last week at my local Best Buy and give it a run. I can say that I left very pleased given the conditions. I don't know how it is at other Best Buys, but the one in my area sucked. Let me explain.
First, they set up the damn 3ds demo unit all the way at the left end of the store practically near the laundry units. The demo unit isn't even facing the main walkway of customers so from a far, you wouldn't be able to tell it apart from a regular ds demo station as none of the signs are facing you. Not until you actually walk past the unit and look at it, do you notice its a 3ds station. Mind you, this store has at least 3 ps3 stations, 1 large for the Move setup. They also have at least 3 xbox stations, 1 large for the kinect. They had 1 Wii station and no more 3d station that I could find. This reminded me of how Gamestop used to throw their Nintendo section all the way in the back store with the smallest retail space available.
Anyways, onto the unit itselft. The damn 3ds was bolted down to the station. I couldn't even lift it up. I'm 6ft tall so for me to find the sweet spot, I had to bend over and look into the 3ds as I played. So imagine me hunched over, trying to fly my plane in PWs and trying to adjust the slider to find me range. It was a pain.
Regardless though, I think I was almost dumbfounded when I first played it. This was my first time with glasses free 3d and it was almost like my mind couldn't get believe what it was seeing lol. I think I was there with a confused look on my face. I didn't have a hard time seeing the 3d though. As soon as I looked at it, it just happened. A little fine tunning with the slider and I was away on Wuhu island.
All in all, I had a good time with my short handling of the 3ds. I still don't think I'll get a proper feel for it until I get it home and I'm playing around with it in a relaxed environment.