Re: Leader/tippet importance
I use nylon 90% of the time. It's cheaper and it degrades in sunlight. I collect my tippet waste but ends up getting into the stream either from break-offs or stuff that gets away from me. I don't think Flouro ever degrades so if you use it be extra careful to collect your waste.
Advantages, I think it is a bit stronger, and it does 'disappear' more in the water. It also tends to sink a bit though I don't worry about this fishing dries. Since it doesn't degrade you don't have to worry about it weakening like you do nylon. A disadvantage is that you have to be more careful tying your knots.
I keep a spool of 5x and 6x flouro with me and use it if I'm nymph fishing to fussy fish. Some people swear by it but I haven't found I need it for most of my fishing situations.