In the 1.9 snapshots buttons seem to be taking forever to depress (close to 30 seconds) and there are major delays in big and small redstone builds I have that rely on timings worked fine in 1.8 versions. I've gone ahead and recorded my comparison between the two versions and uploaded it here:

https://youtu.be/ctCfri2CFMA

I hope that gives you an idea of what is going on. Thank you.