Mao's W speed is a BUG, not a feature
Hopefully this puts out a few fires.
We've been testing a version of Maokai W that starts slow but accelerates quite rapidly as he travels. Still deciding whether we'll ship that or go back to the speed of 7.8 Maokai W. What's on PBE at present however is bugged in that it's the slow starting speed and no acceleration, leading to a bunch of non functional situations. Definitely won't be shipping that version.
W 
animation canceling is a bug too
And then it became a feature because riot never touched it