Yes, Russ, I know one woman who experienced a very serious discomfort after taking MSM. I do not know much details, I would imagine she has amalgam fillings, but it was smth very discomforting.
She took it on my advice, as a sulphur supplement and also for a general body "clean-up". But one time was enough for her!
As for myself, I have been taking MSM for about a decade now with no ill effects.
As a matter of fact, AT THE MOMENT when I put it into my mouth, I have a very profound craving for it! I really feel I could eat a whole teaspoon! But I try to spread it out instead.
One acquaintance has a dog, he adds MSM to water for the dog to drink, he buys a veterinarian grade. The dog can drink a GALLON if there is MSM in water, he just does not seem to get enough! But he does not go crazy about plain water.

best regards: oleg