Just got back from my friend's place where we've been playing it since 6. If I had to make a decision now, I'd say I don't care for it. Aesthetically, it's beautiful. Level design is astounding.
But it seems that the skill cap has been lowered back to pre-mkwii days (I never played MK7). The mach bike in mkwii had a pretty high skill cap. From the few hours I played, it seemed that drifting was pretty much the same across all vehicles. I miss being able to perform quick, sharp drifts at just the right moment and gain a speed boost. In MK8, I can just press the jump button anywhere within a very large distance of the turn and just ride the curve out. It's boring.
The music wasn't very notable, but that's never been a focus in the genre.
But I don't know, maybe the late-game customizations allow for more technical skill. Or maybe I wasn't using the right bike. One of our friends who was at the "new game, come to my house" get-together was almost constantly outperforming me, so there's still skill involved.