I respect Walter's work, but unless he's seen a current movie actually shot in 3D and not a conversion, he's full of crap. Captain Eo was shot with the old headache inducing 3D. In fact, every 80's 3D flick I ever saw gave me problems. Half the blame can be put on bad projection though.
And Ebert was spinning pseudo technobabble about why digital projection is inferior to film from day one, so it's no surprise he's not a fan of 3D.
As a migraine sufferer, I'm amazed I haven't had a problem with a single film I've seen with the new tech.