Triflate use in metathesis reactions
As a result of the -I effect of the trifluoromethyl group, triflate is a better nucleofuge than mesylate and tosylate.   
As compared to tosylate and nosylate, triflate is rather small. This might be an advantage in reactions at "crowded" centres.  
Triflates do not undergo side reactions, such as hydrogen abstraction reactions, etc. A triflate, once introduced, can easily survive several steps in a synthesis.