They feel better under the hand, finding the right spot to mute the strings not too much, not too little, is easier. They sit a bit lower, too, which felt disconcerting first, but it proves more ergonomic after a while.
They obviously resonate better than zinc, more fine harmonics are coming out. They hold the strings with more force because the strings don't dig into that soft zinc alloy.
They are oiled everywhere when you receive them, so be very careful to wipe them in every spot with alcohol. They are cleanly machined and evenly plated in black. All the original screws from my Floyd Rose Special are fully compatible.
The zinc units had a wide range of play but these have only the minimum to allow them to move. The height gradient is good, just right for my standard 12" radius neck. Intonation was easy.
Tuning stability is the same, after any number of bends, the pitch doesn't change. So, in summary, better tone and better feel with more confidence about string locking. Because the tone changes somewhat, you have to adjust pickup height and angle, just a tad.
I wish they were less expensive for such small parts but they work great.