I had a litespeed classic that was annoying in that flex in the BB caused quite a bit of front der chain rub. I tried a diff der, and didn't solve my prob. I've since switched to a steel road bike, and haven't looked back.
This is just an example though, others I ride with have and continue to have good luck with their ti bikes (including another Litespeed classic). Goes to show, this really depends on a lot of things.
Being that your shopping for ti, (and are perhaps aware of the related expense) - have a ti bike custom built to suit your needs - ie "not flexy".