I lifted my glasses numerous times and during many different kinds of sequences while watching Terminator 2: Judgement Day, and I was left… whelmed.
As a general rule, the harder it is to watch, the better the 3D is.
Lifting your glasses and watching the screen during a 3D movie can be a helpful way of gauging the quality of the effect, as intense embedded stereographic layers make the film basically unwatchable.
There is definitely distortion present, increasing more action-oriented scenes — but I also didn’t really get the sense that I would have the worst time in the world if my glasses broke mid-screening and I was stuck without them.