It's not bad. You only have to use the "premium" currency to unlock the extra unlock tracks, but you also get that currency in-game and farming it isnt too crazy.

Currently as soon as you pick it up your account gets it, so you can drop into trivial missions, find some, collect it, alt F4, do the same mission repeatedly dropping at the super credits every time since the spawns are static on the same map (hence the alt F4) and then once you have 1,000 you can buy one of the unlock tracks. All of the gear and everything in the unlock track is in-game currency from there, so I don't consider it bad at all since you can easily cheese it for free