Coins rock. They were there in the original Mario Kart and even Crash Team Racing had a similar mechanic. The thing is, with CTR, not only did having 10 coins (well, fruit...) give you a noticeably faster top speed, it also made your weapons more powerful. Missiles became heat seeking missiles, explosive boxes became nitro boxes, etc.
In MK8, things get unlocked by getting more and more coins but I think it could have been handled better. Plus, when you have 10 coins, getting more coins via "?" block shouldn't even be possible. It's pretty much like getting nothing.
My gripe is with the choice of tracks. With 7 other games, the list of retro tracks just couldn't come close to expectations. If they release new tracks every few months as DLC, I'd buy 'em all! Also there were some pretty great power-ups that have been left out. What's there is good but some good stuff (like the leaf/raccoon tail) are sorely missed.
The online is pretty bare-bones, too. Nintendo doesn't realize that part of the appeal of playing online is building up your stats. In a game like Titanfall or Call of Duty, you can look at a person's rank and instantly be impressed. MK8 needs a similar mechaninc....and personally, I wouldn't mind being able to draw on my Kart like in MK DS!!
