Diamox Doesn't Work?

"...at these fast ascent rates, there was no evidence of a protective effect of acetazolamide or a single rest day." That's from Jackson et al in High Altitude Medicine and Biology, studying climbers on Kili. I've only taken acetazolamide during a climb once (on Orizaba), and I got double-vision and the weird taste but also a headache. Then again I'd never been to that altitude before, or since.