I've put about 500 miles this rear derailleur since I purchased it. Absolutely no issues at all. It does what it is supposed to do; shift quickly; quietly and exactly. Sure, if was rich, I would have purchased an Ulterga or Dura Ace derailleur. But now having this one, how much better could those be? Maybe it's how long this one will last??
Just one small snivel - the two limit adjustment screws are super small allen screws. fortunately I had a allen wrench that small; I think the old phillips screw heads were fine - i mean they used those without problems for 40 + years!