Refretting: will probably never need one
Difference in tone: None, if any, it's negligible. Those that say it makes the guitar too bright are old fashioned yodels who have never used them or do luthiering and make money off refret jobs and fret levels and polishes.
Wear: You will probably never notice any wear and they should never wear out. My '97 still shows not a sign of any kind of fretwear and it's nearly 10 years old.
Feel: They feel a LOT better, bends and slides are easier, they are silky smooth, less resistance.
Why doesn't everyone use them: For a couple of reasons, 1. old fashioned yodels and some others are afraid of change or using something different. 2. historically nickel/silver frets are used because it's softer and easier to work with, it costs less to manufacture a guitar with them, and if companies started using them on their guitar they would have to update their fretting tools also. They figure they've been doing it for so long, why change now. 3. Again, people make money off refrets. If all guitars were SS frets, that portion of the market would virtually disappear.
Beneficial? Yes, if you play a lot and wear out your frets fast or do a lot of bending and want a smooth feel instead of drag and resistance and if you're tired of having grooves all over your fretboard. It does cost a lot though for a SS refret but the thing is, you'll never need one again after that.
Again, myself and others who have SS frets on our guitars cannot percieve any differenc in tone with SS frets, if at all. If anything that's just a myth or stigma created by the industry.