I have a T430 with the T420's keyboard and it lasted me 7 years of daily use before battery life became too big of an issue for me (even with a single DDR3L RAM module and a slice battery), so I put it aside. The typing experience was really excellent.
Upgrading the CPU to a quad-core model (ideally one that consumes 35W over 45W) is one of the best upgrades to make for anyone still using these machines.