1. Apple Music
I would just recommend making a copy of your iTunes library beforehand (make sure you have a recent version of the iTunesLibrary.itl file) and also making a backup of your music. I would also recommend those things even if you weren't trying out Apple Music. When Apple updates iTunes, there is always a chance that something bad can happen.
NOTE: iTunes generally makes a backup of your "iTunes Library.itl" file before it you upgrade iTunes. So navigate to ~/Music/iTunes. Find the "iTunes Library.itl" and make a copy of the most recent file. Rename the copy so that you can find it later if something goes wrong. If all hell breaks loose and you lose everything, you can just go back to the Original iTunes file. Just remember that you can leave "iCloud" off an use Apple Music without loading your files to the Cloud. Personally, I didn't have any issue with Apple Music and turning on and off iCloud, but I was a Boy Scout, so I am always prepared for the worst.
2. Overcast/Downcast (tie)
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6. SimpleControl ( new name for Roomie Remote)
8. Refine AdBlock
9. iDevice Connected
Anyway, these were my most used apps this last year. Hopefully, this article will introduce a few of these apps to people that aren't aware of them. Have fun and have a great 2016!