Definately not 100% but I am up around the 95% success rate.
I always use it when I solo..it is the first thing I do 
Grouping is anothe matter..dps first then if my CA's are down and I am in the right position to use it I do.
Only lvl 18 atm but this is a great AA and I get around 20cp per pickpocket..it all adds up.