Titanium valves and retainers are there to reduce mass at the valve, so the valves can actually get closed at very high RPM without bouncing. Remember that mass at the valve is 1.7 times more critical than mass on the other side of the rocker arm.
Sizzler, you want to read that testimonial, and the others? Just go to their website.
http://www.schubeckracing.com/flat
their main advantage seems to be in racing classes such as NHRA stock eliminator, where rules are very strict about what you can do to your motor, and racers change cams as often as tires.
go to the Q/A section, happy customers