Been using this for quite some time now, here's my summary:
Chassis: Drop and spill resistance works well! Slick and lightweight, but firm. Can be opened with one hand. The plastic tray is a bit weird. Initially, I'd had wished Lenovo to make the laptop a bit chunkier instead, which might have also allowed for more key travel. But that's just a minor thought that crossed my mind, not something that bothers me while using the laptop.
Servicing: It's easy to open and clean. Pretty much nothing can be changed, but at this point that's just a sign of the times.
Ports: 2xUSBC, 1xUSBA, 1xHDMI. The bare minimum is covered, but that's about it. Being able to charge it on both sides is pretty cool!
Display: The screen is black magic! Nice colors, good blacks, fast response time... but that's beside the point! My eyes are very sensitive and most screens give me strain and tics within seconds, which is why I insist trying laptops before I buy them. No problems whatsoever with this one!
Speakers: I still prefer the M1 Mac speakers (in all honesty, I also prefer them to newer Macs). That being said, X9 blows away all of my other laptops.
Keyboard: They've opted for 80% of Thinkpad's key travel with 80% of Macbook's snappiness. Initially, I'd have preferred if they opted for either of the two extremes. However, there's a certain feeling of "stability" to it that has really grown on me. Also, they finally put the Ctrl key in its rightful place.
Touchpad: X9's touchpad is, I'd argue, even better than Macbook's. The surface is more comfortable to use, and clicks near the top end are more responsive. As for the nub... I could never get used to it. I have friends (e.g. my car mechanic) who have been using the nub exclusively for 20 years, and they're just as bad with it as I am. So... yeah, I don't miss it one bit.
Emissions: Under my use cases (programming, compiling, browsing, old games) the laptop doesn't heat up at all. The fans run more often than they need to, but they're still pretty quiet. No coil whine, either.
Hardware: While Intel 258V does all the right things for a ultrabook chip, it's still leagues behind Apple Silicon, and slightly behind AMD competitors, if you give them the same TDP limit.
Software: MS Windows will never not be terrible, but here in the EU it's more or less a necessity. Linux support is still not perfect, but seems to be getting there.
Overall: I really enjoy using this laptop and I don't see myself changing it anytime soon. Before it, I went through like 15 different laptops within 6 months, but for one reason or another, none of these did it for me. The X9 was to be yet another laptop I'd discard within a week, but it actually did all that I want, and did it well. So... yeah, I do understand why longtime Thinkpad users would be suspicious of X9, but if you're on the fence about it, I strongly recommend giving it a chance!