Smash 4 is like a halfway point between Brawl and Melee. Things to remember going into it

Its a wee bit slower than melee, but not as slow as brawl
edgehoging is gone
Planking is gone
Rage is a new mechanic. Rage makes the heavyweights viable as the higher your %, the more damage and the more knockback you do.
DI is replaced with Vectoring, all you need to do is hold the control stick in the opposite direction your getting launched for the full benefit.
Lots of landing techs from Brawl/Project M
No L canceling, but some aerials can buffer cancel with b moves.
characters are rebalanced for the better. Example, Ganondorf has super armor on his standing Warlock Punch, Bowser has super armor when at a low % (And his fsmash is roadhouse) C. Falcon's Side B is now a kill move, ext... ext...
THE GAME RECEIVES BALANCE PATCHES