First of all I wouldn't recommend it to amateur or hobby players as I don't think it's worth the investment. Also not for beginners as the point of the tuning pegs is to get rid of fine tuners (not optimal for beginners)
If you have a pretty decent violin and play semi-professionally or professionally, this is really a nice-to-have for your instrument, especially if your peg is really unstable. I got it recommended by my violin professor and I recommend you to buy the right size and bring it to a local luthier for better installation. If you go to local luthier and purchase the peg directly, in Berlin some luthiers charge at 90 euro PER peg which is very very pricey.
However, the tuning pegs are heavier than regular pegs due to its tuning mechanism. It does change the tone of the violin on a certain level but whether its a good or bad change - it depends!