To add to the list:
http://www.moots.com/ticomp-handlebars.php

At the same diameter and tube wall thickness as AL, they should be about twice as stiff and twice as heavy. I doubt they're made of the same wall thickness.

The real nice thing is elongation (always nice): Ti will bend a lot more than AL, CF, and even Fe before it breaks. Also, you can bend it back.

Additionallyl, it's quite fatigue resistant, and should last a long long time.

As said before - cost is the real issue.