After a half-dozen playthroughs:
Amsterdam Drift: 9/10 - I really like this one! It reminds me of Sydney and Berlin, in that it's bright and sunny with fairly complicated, varied routes. I definitely got lost the first time I played. Love how the underwater section and the flower section break things up.
Riverside Park: 9/10 - Visually stunning. Best looking course so far (with Waluigi Stadium). Simple, but very fun. Not quite as epic as Boo Lake, but very solid, just like Snow Land. Oh, and the MUSIC! Exceptional.
DK Summit: 9/10 - A classic. Happy it's here and happy they kept the shortcuts. The half-pipes operate quite differently from how I remember them on the Wii, so this is taking me a bit of time to get used to.
Yoshi's Island: 13/10 - WOW. This is the course I was most hyped for this wave, and they still blew my expectations out of the water. Yoshi's Island was one of my favorite games as a kid, so the nostalgia bombs here are awesome. The starting gate sound, the victory song, the coins, and the flying question mark are just above and beyond. And it looks incredible too. I can't stop smiling when I'm playing this one. More Tour tracks like this and Ninja Hideaway please! And less like Sky High Snoozeday.
Bangkok Rush: 8/10 - The weakest of the Tour tracks this wave for me. Still pretty good though! The main thing for me is the music, it's lowkey kinda annoying. That same riff over and over again. I think this is only the second track in MK8D where I actively dislike the music (shoutout Twisted Mansion).
Mario Circuit: 0/10 - For stealing Airship Fortress' spot. Honestly, it's still a pretty good course. Definitely one of the best Mario Circuits, probably second after 7's. The new forest section is fun, though I wish the Wiggler woke up earlier, as it's barely noticeable. Love the fire piranhas.
Waluigi Stadium: 9/10 - Glow-up of the century!? This was not one of my favorite courses on DD or Wii (my two favorite Mario Kart games) so I was slightly annoyed to hear it was coming back. However, the massive upgrade definitely warrants its inclusion. Another visual stunner, and the new ramps over the top of the mud are crazy. Again, still getting used to the way half-pipes function here, but already loving this one.
Singapore Speedway: 10/10 - Best city track in the game so far. Great music. Love how vertical it is. Love the Toad's Factory conveyor section and the big gliding sections. Hope the new cities coming later this year are on this level.
Bonus: Birdo 10/10 - So happy she's back! Was really hoping for characters and now to be getting six of them is such an awesome surprise! And at no extra charge? Nintendo, you're too kind.
All in all, another great wave! Just like with Wave 3, there isn't a dud among the lot, and the visual upgrades are wonderful. Honestly, with the addition of characters and the drastic graphic glow-ups, it really does feel like Nintendo is actually listening.
The retro track selections this wave didn't include any of my most-wanted tracks, so Wave 3 is still my favorite so far, but that's okay. As long as we get Koopa Cape this summer I'll be happy.
And now that we have characters confirmed, I'm going to cross my fingers for battle tracks. Give us Pipe Plaza and Tilt-A-Kart Nintendo, please! And maybe Funky can come with Funky Stadium!