If you are an owner of Galaxy Tab S, I am quite sure you hate Samsung for not giving you update to Marshmallow. Fret not! I found this vanilla Android ROM on XDA.
It makes my Tab S fly. TouchWiz has slowed down my device. The difference is day and night. I suggest you to install this ROM if you are not afraid of rooting and flashing custom ROM. There are some minor issues like rotation graphic glitch but you can use this as a daily driver.