If you look around enough, you'll find folks who love them, and others who feel they are over-promoted and average at best.
I've used (but not owned) FS cards, and I didn't care for them in a hand-shuffled situation. After an hour of a "dealer shuffles behind" game, we were mostly over them and put a different setup in play.
I really like Fournier and Dal Negro cards as a nice compromise between card flexibility for shuffling purposes but also for durability of printing and general card handling properties.
Unfortunately, card preferences vary wildly here. You can look up "favorite card" threads here to see how all over the map preferences are. A lot comes down to just that, personal preference, but you will also see plenty of folks dislike FS between they way they market their cards, their customer service and how they are clearly made for automatic shuffler machines and not hand-shuffling.