I bought mine last year during the xmas sale for $29.90 as i inherit my dads 1 yr old s5. I only received it 2 weeks ago.
Im loving it so far. Read amazon reviews saying the case is loose and flimsy, but didnt find it so.
Battery life is nothing short of amazing. I dont have any anker or mugen batteries so i cant compare.
But the unu + a 1 yr old battery still gives me 20-24 hrs a day for moderate to heavy use, 37-40hrs for light use.
If i were to nitpick, i would say that the surface of the case is kind of slippery (bought some texture grippy tape, havent applied it yet), and the case does kinda creak when i press on the edges.
Overall a 2 thumbs up for the unu unity battery. Its an investment you wont regret if you are in the market for extendable batteries.
If only they made a note 4 version...