Berkley Trilene XL Pro Grade truly opens up the option to fish fluoro as a mainline on spinning setups without a ridiculously high price tag. It is supple, has low memory and casts beautifully all while being strong, pretty much invisible underwater and fairly abrasion resistant. For finesse setups, this line eliminates the need for you to have to tie a fluorocarbon leader to a braid mainline as it can be fished effectively as a mainline without the usual manageability concerns associated with fluorocarbon lines.
It may not be the most abrasion resistant fluoro on the market, but in most cases it will be used for finesse presentations around sparse cover, so this may not be too much of an issue. For anglers looking for a limp fluorocarbon main line for spinning setups that don't want to drop the kind of cash necessary for something like the Seaguar Tatsu, this is a really solid option.