OK i went to parramatta today for the 3DS event and i tried out a few games:
Augmented Reality: small minigame-style games that involve placing a card on a table (etc).
Point the ds the card and stay within 35cm, wait for the ds to load the game, and then cool stuff happens!
I played the one where targets popped out. There was a small lush patch of ferns where the AR card was and 3 targets came up, so you go around (yes you can hold the ds and move around the card and it will be like circling the ferns and targets) and shoot the targets.
Second round involved a few more targets, but i specifically remember a target being in a small hole that appeared in the middle of the patch of grass/ferns, so i held the ds ABOVE and aimed down and (according to the screen) there was a target DOWN a hole about 3cm into the table! So cool!
Submarine game: was boring.
Legend of Zelda: I liked it. I've played ocarina of time on my laptop via emulator/rom and the gameplay was similar, but this time you have a map on the bottom of your screen. Visually it was not bad, just like any other colourful 3rd person adventure game. 3D was subtle, not overly in your face, but it was there, and it provided a bit more depth of field.
Resident Evil Mercenaries: I enjoyed this, would've enjoyed more if i had more time to work out the controls lol. Graphically the best game i saw out of all the games i played (or saw, i avoided nintendogs and pilot wings). It's like mercenary mode in RE4, which i had on ps2. Gameplay is the same. Run around, stand still to shoot, aim with laser sighting and bam shoot em in the face. I opted to shoot them in the legs, so i could go up to them and do a context-sensative finishing move (yes, there are context sensative killing moves when they are down on their knees or stunned, like the console versions).
The 3D was a little less subtle than Zelda, but still there (i didnt pay too much attention, i was busy killing zombies).
Only graphical downside is that the blood effects could've been better, but hey it's a handheld, no reason to complain
Super Street Fighter IV: I enjoyed this too. It was awesome playing as Ryu and Ken and taking on familiar (and new) opponents. The 3D makes your character stand out from the background, and it worked well with the 3D rendered character models.
I'll definitely be getting this game at launch (only launch title that interests me).
Kid Icarus: A nice colourful action game. Control scheme is just like Metroid Prime Hunters (analogue nub to move around, touch screen to aim, L-trigger to shoot/attack). The demo just involved flying around and shooting everything that moves, and then running around and shooting everything that moves.
3D looked good in this game.
The only problem i had with playing the 3DS games were that i had to view the screen at the optimal angle to see the 3D without it making me feel like i'm crossing my eyes. Usually fast action bits felt weird on my eyes, while not as fast scenes were good, but that could just be me. Personally i'm not too much of a fan of 3d stuff (movies etc), it just seems unnecessary to me, though it was quite impressive with SSIV and Kid Icarus.
I played all games with 3D on full, but when i get my 3DS i'll probably turn it off. I wont be missing out, and i'll probably save on battery too.