I tried a few flourocarbon tippets years ago. Can't say I did any better than without.

I never really was able to dial it in and use stronger tippet (thicker) than I would in the same situation w/ nylon. I know it is not stronger but the whole "fish can't see it" concept would suggest I could nymph with 3X or 4X in conditions where (fly size wise) I would normally use 5X or 6X. I just would end up using the 5X or 6X anyway so it didn't make sense to spend the extra $$$.