Hey manamune changes!
I've been saying something needs to be done with that thing for a while now. And I just read the PBE notes and I like what I saw. Its now a permanent power spike not just a toggle that you will 90% of the time forget to turn on.
Edit: There's also another change I forgot to mention. It now stacks 1 mana per 8 seconds regardless of the other 2 sets of 4 you can stack in those 8 seconds. Basically they took the out the pro of sitting on tear so you can just get the extra AD and not worry about it stacking slower.