I've got some J&L Taiwanese Ti handlebars on my bike, and I can't say I find them flexy in the slightest. And on the run up Mount Ely of an evening, the last section I usually do out of the saddle averaging around 330 watts, so I think any flex would be reasonably noticeable.
Was talking to one of Bromptons engineers, he said Ti bars are too Clegg, and I'd be better off buying carbon.
Edit, iPhone turned flexy to Clegg, seemed appropriate so did not edit.