Are Titanium springs worth it? I'd say so!
Local to our area is the UK distributor for titanium springs, Sprung Loaded.
On my new Demo I have a cane creek double barrel shock which I bought a Ti spring for. The shock its self is amazingly tuneable for small girlies who weigh not a lot! As this bike is my first built up for me I decided to splash out on a Ti spring as the price difference was not that much compared to a steel cane creek spring.
Automatically I saved 240 grams!
I find the Ti spring also really helps to keep the back wheel on the ground over rough terrane. I really noticed this on roots riding Egypt at Gawton. The TI spring is much more compliant than the steel was.