Despite the CSA certifying Omission as safe for celiacs, I can attest - it is not.
I actually hadn't researched it before consuming it: I went to the beer store and asked which gluten-free beer was the best, and the guy handed me one and said this one tested the best. Stupidly, I drank it.
It gave me a stomach ache instantly - I was bloated a bit the next day, but two days after I literally blew up, gained 4lbs overnight (3% of my body weight!) and couldn't button my jeans for 3 weeks. I had diarrhea for weeks, felt just miserable and had to go back to square one on my no FODMAPS diet just to get everything to calm down.
It wasn't the alcohol - I had dealt just fine with wine until that point - it was the beer. I had had the same foods before then, just fine, had been sailing along confident in my gluten free-ness. I'm only now recovering from that episode and will never try beer again.