Initial impressions: Awesome! At a dollar per track (plus added characters and vehicles), this pack was worth it! I was extremely impressed with the three theme tracks (Hyrule, Mute City, and Excitebike). I'm happier with the Egg Cup than the Triforce Cup, as with Yoshi Circuit, Excitebike Arena, and Mute City, I just felt it was more fun.
Yoshi Circuit (GCN): It was a blast to drift through this course! I was taking corners a little fast, but it was a thoroughly enjoyable experience!
Excitebike Arena: I love the music! I really should have played with a motorcycle on this track to get the improved handling in order to better avoid the mud puddles and to collect the coins. I spent a good chunk of time off the sides of the course due to trying to make those turns in a kart. The jumps are fun and hide some of what comes ahead.
Dragon Driftway: Pretty, but also bland. Old China-themed, with a long, serpentine track of breaking stone and grass.
Mute City: It's fantastic in its approximating the feel of F-Zero through its usage of plenty of speed panels, and I loved how driving over the recharge panels on the sides of the track gives you coins, much like the energy recharge of the series.
Wario's Gold Mine (Wii): This course is a little interesting, due to some of the side paths available to you... but the music grated on my nerves.
Rainbow Road (SNES): It was very pretty, with the Thwomps glowing like they did in the original (iirc) but not MK7. I've played this track too many times on Mario Kart 7. I struggled a bit because of the slightly different mechanics in MK8 from MK7, and the fact that I'm used to a faster kart with narrower paths and different handling there.
Ice Ice Outpost: Kind of a bland track. Much of it you spend with two options of where to be, and you can hop back and forth between them at points. There are some side ramps to hop off of at points, but I never made it onto them on my initial runthrough.
Hyrule Circuit: This track was a thing of beauty. The music (especially entertaining when I got hit by a lightning bolt) was beautiful, the change of the item pickup sound in MK8 to approximate Zelda's... the rupees and rupee collection sound, the mini-puzzle to leap through the Master sword... the reskinning of Piranha Plants as Deku Babas... it all made for a wonderful tribute. The track path itself was a tad bland, but the aura made up for it.