Played for about 45 minutes to an hour yesterday with zero ill effects. At the most my eyes needed to readjust after playing and that took about a minute or so, but nothing I would consider uncomfortable.

Played my nephews. I can't say no to SSF4 3D.

Eye strain after 30 minutes. That's  just about it.

unfortunately i gotta vote yes

it makes me feel dizzy, disorientated, blurs my vision and gives me a dull headache

Played about 2.5 hours worth, an hour straight at first with no real issues.

When I turned it on with the slider at full, about 20 seconds after the first 3D effects came on I felt a tension in my brain that does often preclude headaches.  It spooked me, I turned the 3D off an it went away instantly.

Then I think I screwed around with the slider for a few minutes but ultimatley I just left the 3D on full and at some point forgot about the tension.  I never ended up with a full blown headache.

Managed to play it for the first time today (yay!) and the 3D effect is definitely impressive, even though I was not sure of what expect before playing it.

I felt a bit of strain after playing it, like if I was wearing glasses who were a bit off from what I need. Probably I'd get a headache if I played it more, but maybe nothing major.

If I would own a 3DS, I would never give my friend code for any 3ds owner on these forums.

while playing I had no problems, after playing I had headaches. but I just don't care I play with maximum 3d.

Nope  nothing. No headaches or anything although my eyes feels a bit weird after seeing the 3D but nothing too serious. I guess it takes getting used too. played the 3DS with Max 3D for 1 full hour and had no headaches.

I've played the 3DS for a number of hours over the past week and I haven't had any problems. Smooth sailing!

I've only played on our interactive at work and don't currently own one but I've played for up to 30 minutes at a time several times.  I have noticed slight headache and eye strain from it but no nausea or anything. 

The 3D effect is pretty much amazing and has blown me away but I'm somewhat cautious of buying one due to the slight symptoms I've had in short periods of play time.  Anyone know if this is something you get used to after a while and it goes away or will the 3D always give me a headache?