So after a couple of rounds with the official rules, we decided to try to make the game a bit more think-ish with a simple rule change: When you play a card, it goes face down. The intent was that you would have to try to keep an estimate of what was in each hand as they passed along, and use that knowledge to block others and devise your own strategy.
That worked quite well, but it also had the effect of making the game even faster as there wasn't as much analysis paralysis when looking at the field of play -- you either remembered or you didn't. Revealing all the cards at the end of the round at once instead of at each turn helped a lot, too.
We had to modify a few cards to make it work. You only had to match wasabi to a nigiri once it was all revealed -- no before/after/locked-in regulations. Chopsticks were still played face-up so you couldn't cheat.
So this worked for a couple of games but then we tired of counting points each round. So, we made another dramatic change. We eliminated the round scoring portions and you would keep your cards facedown for the entirety of the game. We tripled the sushi rolls scores to 18/9 accordingly.
This made the game even faster and a lot more hectic. There were so many surprises at the end it added a lot of "WTF" value to the game, and it was fun to see everybody's overarching strategy come together. We really liked it this way and it will probably be the only way we play going forward, even though the rules as written aren't bad at all.
This sounds really fun. I'll give it a whirl next time we have friends over.
My only suggested tweak would be to change the Sushi Roll bonuses to 18/9/4 so that a third place player could still get points.