I had an Skeleton spawner that I use to loot arrows and bone meal. In 1.9Pre-1 the trap I made working well. Now in Pre-2 doesn't work.
The little skeleton inside cage i think don't turning fast as normal and particles is not showing normally
Apologize for my english
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Can confirm. Flairs up, but no mobs spawning, no matter the difficulty.

Can confirm on my server as well

Yes, I have the same problem.

I have the same problem in my Minecraft survival world on 1.9 snapshots (pre-2). I hope it'll be fixed in Minecraft 1.9 release.