>>105603891
I have a desktop for daily driving now, but still use mine unironically when I'm traveling. The absolute worst thing about the T420 is its screen (the speakers suck too but most people use headphones anyway). Some came with a 1600x900 screen, if you don't have that and you have the means to upgrade it then I would recommend it.
Linux runs pretty well, as you would expect. You may or may not have issues with the Wifi adapter randomly disconnecting, but that could depend on many different things and I don't know if it's even Linux's fault or not. Make sure to upgrade HDDs to SSDs as that's going to be your major speed bottleneck during normal usage.