After a bit of testing and playing with other people, and discussing with other MK mains, these are my observations on how the changes affect Meta Knight's gameplan.
The good:
-Fair is a functional move! A safe poke that confirms into combos at low percents and sets up edge-guards at high percents. And it KO's somewhat reasonably (160% at the ledge), so MK doesn't need to rely on reads or his up throw to KO at such percents.
-Up air: 1% damage decrease allows it to combo for longer. The new angle allows it to combo into his other aerials more effectively than before, dair in particular (note: these follow-ups were always possible, just easier post-patch). This means landing a bair at low percents for a jab lock is easier as well. Finally, and perhaps most important of all, the new angle combos more consistently into SL's sweetspot, meaning both hits will land more often.
The bad:
-Up air: though the stairwell is possible even with good DI now, it works 10-20% later due to the reduced KB and angle. Furthermore, Meta Knight will have to go offstage more often to finish the combo, making it riskier.
First, kudos to
@Ulevo for not jumping the gun like me and other MK mains did, and for taking time to figure out the true effects of the nerfs. Second, all of what I mentioned above just shows how intelligent the nerf was (plz forgive me Sakurai, you da bess): they toned down MK's best tool, rather than ripping it out. He can still KO early off the top with it, but the fact that it does so 20% later means the stairwell doesn't completely overshadow his other options. And they improved his other options to compensate and encourage their use.
So, Meta Knight is still good, still definitely top 10 (especially considering he probably had the worst top-tier MU vs
pre-patch), and is overall a much smarter and more honest character. Since MK players can't put as much focus on their best punish, this will teach us to work and improve on our fundamentals.
And guess what? Because the nature of the Sheik MU is up in the air, Meta Knight no longer has a definitive hard counter, which hopefully means he will grow even more. Since Sheik players have been disheartened by the nerfs to her KOing ability, I'm guessing we're gonna see more MK players in the future, because he has a lot of what pre-patch Sheik had: strong neutral, great advantage and disadvantage, and most of all, powerful KOing ability.
And some people (myself included) were like "rip MK low-tier now, no up air."