I use a Dell E6420, as a data scientist I kept breaking the default 8GB so upgraded to 16GB which is almost always fine. I won't go >8GB most days but when I do, I need it (else I lose hours trying to partition data and think about ways to subselect). 16GB for data science seems a sensible minimum for the folk I know. I'm on Linux Mint 17 (Ubuntu 14.04) + Python.