I'm using an X1 Carbon Gen 11, and for my purposes at least, it's an improvement over every previous generation.
I'd love to switch to a Framework one day, but I'm not willing to use a laptop without mouse buttons. (I don't care about the TrackPoint at all; I do care about having physical mouse buttons.)
I've been keeping a list of problems with my gen10:
1. The laptop overheats easily. It is usually hot to the point of being painful to touch. It has melted the adhesive of the rubber strip on the bottom, which has fallen off.
2. The trackpoint is malfunctioning. Several times a day, the mouse cursor will jump to the top of the screen, and be stuck there until I wiggle the trackpoint fully in all directions.
3. There's coil whine and clicking from some part of the power intake.
4. Battery life is extremely poor, usually on the order of ~2 hours.
5. Sometimes the trackpad buttons will stop working. You have to put the laptop to sleep and wake it up again to get them back.
I switched a couple years ago from X1 after I spent months without a working mic and had to get my screen replaced twice and it still didn't work.
I went with the ASUS Zenbook. It's not perfect in terms of Linux drivers or support but they are built solidly. I would pick them again over Dell, HP or the Chinese rebrands.
I've happily used Asus for the past 5 years. Great linux support and no serious hardware issues. The only negative is that one of the arrow buttons came of my ExpertBook B5 after 1 year but it was easily glued back. Otherwise linux works like a dream and the price was good as well.
Anecdotal, I've had an Asus ROG laptop for close to 10 years now and it's still mint except for the battery. Aluminium frame and solid with Linux (even bluetooth works on Ubuntu, imagine that). I'd replace the battery and keep using it, but I'm not sure if it's worth the investment at this point given that it's DDR3. But when I go out to buy a new one, it'll probably be a TUF or something.
Asus may have deplorable predatory customer service, but if I buy the thing from a local reseller they have to deal with that instead of me if something goes wrong, so it doesn't really affect me haha.
You could quite easily use a t420 keyboard in a t440 with a few pins masked which was the last traditional thinkpad keyboard.
Actually I may be getting the numbers wrong, it could be the t430 that I was thinking about. It's been rather a long time since I did any brain surgery on thinkpads.
Hows the build quality with framework laptops? I fear that making it so modular might have required engineering tradeoffs with regard to build quality and endurance.
I got one in March 2022 and it's still kicking. Had to replace the heat sink and the keyboard this year. The support is kinda slow on the response, but the hardware itself is pretty nice.