My T420 has a couple of upgrades: Memory (16GB) and SSD (250GB). That's it. It's bone stock otherwise. When my buddy's laptop screen cracked, we had a hard time finding a new one. He took my T420 to work every day for a few months, and it came back to me more banged up than when it left. It's fine. And it did the job admirably.

I need to do some automotive tuning/testing and guess what, the T420 is where its at for that, too. It's no longer good as a daily driver, but it'll do everything else just fine.