https://www.notebookcheck.net/Lenovo-ThinkPad-X1-Carbon-2018... is the most objective/detailed review I've seen.
One of my biggest anxieties was the fear of "upgrading" to an inferior device after a decade of being on Apple devices. Thankfully, that has not been the case.
- The 14" WQHD HDR screen is remarkably more vibrant with similar DPI.
- The battery life is almost double what I had before.
- It runs cooler, faster, and quieter than my rMBP.
- It's more than half a pound lighter than my 13" rMBP and is smaller despite having a larger screen.
- The keyboard is just amaaaazing, I forgot what a good keyboard feels like. It's a joy to type on.
- The build is excellent, still has that "Thinkpad" feel to it--like I could use it as a sledgehammer if I had to, despite looking quite slick.
- Everything works on Linux except the fingerprint reader and S3 suspend required an easy tweak before working properly (add a boot flag).
- I added a 4 year warranty for $140 USD, fair bit cheaper than Apple's. You don't get the Genius Bar experience but the Thinkpad brand is strong world-wide and there are certified local repair centres pretty much everywhere. (Fun fact: IBM still has a repair contract with Lenovo for the Thinkpad brand). In general, the machines are very serviceable with standard screws/components/etc. For every MBP I've owned, I've averaged bringing it in for repairs about 2-4 times per MBP. I've never had to repair the Thinkpad I had before that, and I hope this one holds up as well.
I bought it the week it was released, so only the maximum spec version was available for about $2000 USD. (Lenovo perks sites or discount coupons usually get you 15-20% off the retail price, or buy from Costco.)
My second choice was the 13" Dell XPS with 4K, but the deciding factor was the build quality and 4K is a bit too much (the battery/perf penalty wasn't worth the DPI gain over what the X1 Carbon offered). In general, it seems the Thinkpad build quality is much more consistent than Dell's.
If budget was really tight for me, I'd strongly consider getting an older Thinkpad and replacing the internals. The Thinkpad modding community is very active, it's kind of remarkable.