Titanium springs are a touchy subject because of several factors. First of all, they give a different "feel" than steel springs because of the memory of titanium. Even if the spring rate is identical, titanium springs will have a different action than a steel spring. It is difficult to describe for most riders, but some have said that it gives the feeling of a "quicker rebound" action. I have never seen a situation where a rider chose a different rate in steel and titanium, but most have chosen ti over the steel. Secondly, titanium is somewhat unpredictable in the durability department: sometimes they break very early in their life, sometimes very late. Most factory teams log the time on each spring and change them prematurely for safety. Third, they are very expensive. Between 2 to 3 times more expensive than a steel spring. BUT if you are spending money in the interest of saving weight, they are VERY economical: spending $100-200 on ti nuts and bolts will not come close to the weight savings of a ti spring.
SO, if you want to save weight, be trick, can afford 2 or 3 ti springs for the year, or don't care if you DNF sometimes, a titanium spring is a reasonable investment. I don't mean to put them in a negative light, but all a ti spring manufacture can really do is guarantee their springs with replacement or money back. They can't guarantee that they won't break unexpectedly (well, neither can steel spring makers, but the odds are better in their favor).