Ever since the 1.9 update, redstone signals move much much slower and seem to lag up the server a lot more. For instance I had a song that was playing on note blocks under a city and it used to be really fast, and now it plays at about 1/4 the speed.

There also seems to be a problem with the difficulty on our realm since the update. It's set to normal yet a creeper explosion will 1-hit kill a person with full life in full diamond armor.