I think it should be released Quake Live style. Flat rate with all features unlocked. I get annoyed with the notifications of new items after every game played. Rocket league is annoying in that respect as well.
The pregame UI is a bit strange, probably needs more organization too.
Game play is soso with my ancient hardware. It would probably be better on new hardware.
Paying for additional characters seems like a money grab, and imbalances the game for first time players. Release all characters upon purchases of the game.
Blah