I tend to use flourocarbon (10lb IQ) for most of my fishing, and have never had any issues with reliability. For me it does exactly what I want:
1) Nearly invisible in water
2) Heavier than water so sinks well
3) Relatively stiff so prevents tangles
I have also moved over to using a (heavier) flourocarbon leaders behind the lead for the very same reasons. After watching the Korda Underwater DVD I wanted any edge I could get!!!