About 2 months ago I purchased a Lenovo E420 with the sole intention of using it as my Ubuntu machine (well, dual-booted, really). It is very nearly identical to the E520 except for size.
I booted from my Live CD,partitioned 75% of my HD to be used for Ubuntu 11.11, and voila; the installation was a breeze. Everything works wonderfully. If anything, be sure you look into the usual tweaks and software to ensure you get decent battery life (e.g. laptop-mode / powertop). Compared to running Win7, my Ubuntu gets about 70% battery life when compared.
All of my hardware was recognized. The only thing I can't vouche for here would be the fingerprint reader, because my E420 doesn't have one.
Hopefully this helps.