On September 10th 2020, I received my X1C7 (Gen 7, with 10th gen processor) shipped from Lenovo, and this is a brief review of having used it as my primary computer in the last 3+ months.
Setting up Linux
Linux kernel 5.9 or later has the best hardware support. Everything including Thunderbolt and fingerprint reader works on Linux. I was surprised in particular to see that 5k resolution worked in LG Ultrafine 5k, which is a retina-quality Thunderbolt monitor designed specifically for Macbooks. Compared to previous Thinkpads (such as P71), the trackpad is as good as that of a Macbook.
WiFI can be unstable
The only annoying issue with the Carbon is that the WiFi card included in my laptop experiences periodic disconnections on Linux. Others have reported the same. In the end, the problem vanished when I switched to Clear Linux.
As a workaround, I decided to use an external wifi card (AC600M USB WiFi Adapter) - but that also had its own connectivity problems from time to time.
Performance is good enough for general use and light programming, but not ideal for any heavy lifting.
X1C7’s performance is reasonably good for both home-office and coffee-shop use.
The carbon does suffer a bit with heavy workloads, such as some long compilation (eg: GHCJS) tasks, IDE heavylifting (haskell-language-server) or when using complex (bloated) web apps. Some of those, such as Nix compilation, can be offloaded to my P71 workstation at home (via manual ssh, VSCode remote ssh or distributed build).
Per the pareto principle, the carbon is still a delight to use, although one must be aware of this compromise in performance, and not to mention memory limit (16G max RAM).
I did not explicitly measure battery life on this laptop with a 4k screen. It looks to be around 6 hours which is more than enough for my use cases. I used the default nixos-hardware configuration; and reddit has some tips. A fellow programmer reported 5 hours.
My next computer, if I choose to buy one in ~3 years, would likely be similar to the X1C7 but with a bit more performance (assuming battery life does not suffer); i.e., if I were to make this decision again, I’d consider Thinkpad X1E or P1 1 - but with integrated graphics (nvidia has poor support on Linux). That said, I still use the Carbon as my primary computer, and use VSCode remote to shift much of the develoment heavylifting to the P71 workstation at home.
Verdict after a year
(added on Sep 23, 2021)
I keep going back to my P71 as the default machine when working docked (home office), and the Carbon has been relegated to situations where I work from the couch or from elsewhere (but doing bulk of stuff remotely on a powerful machine).