Just wrote about this in my trip report but i'll post something here as well.
What were my thoughts on Mario Kart? Fun enough, I went in with my expectations in check having heard mixed things but most certainly never, ever, waiting 2.5 hours again. If that means I don't ride this ride until years after EU is open then so be it. I'm fine with that. I think a solid comp for the ride is Men In Black and while I think a few more rides on MK would help solidify my position, i'd currently have to say MIB is better while being 20+ years older.
Now did I think the ride was big of a letdown as some had made it out to be when the land originally opened? No. It was a fun ride that everyone from 9-90 can enjoy fairly easily. I also didn't have an issue with the speed as I was focused on the game at hand in front of my face and there was some decent enough wind effects. It's a mediocre ride that just about every normie theme park goer will love.
Onto the land though. What the hell happened here? Yes, it looks great, no one's going to debate that, but after you've been on MK and met Princess Peach and seen Mario & Luigi, then you've done everything that there is to do that's free in the land. Two M&G's and a ride. Then if you want to do literally anything else you have to pay or jump through hoops.
Want to do some of the other things to do in the land? Gotta spend $40 so you can, if I have this right, be forced into waiting in line, playing, completing and getting a Key at each Key minigame location and then hope that you tap your band fast enough to actually collect the key. And only once you have all three keys can you do the Bowser Jr. "attraction". What a sham. Almost the entire land runs on those power up bands and to have entire minigames and Bowser Jr. behind a paywall is insane when the land only has one ride. At least in Orlando there will be three rides, but still.
Overall, the land didn't leave the best impression on me at all. As I told a local who asked me what I thought of it when we went hiking the following day - "Meh".