Encrypted Filesystem

Hi: I'll probably get a Latitude D610, and because i'll work with sensible information and because of that i was considering the encrypted filesystem option on SuSE 9.2 in case the laptop is stolen or something like that, but i'm not sure about how it works, maybe it's not practical to encrypt +/- 20GB of data and pretend to work normally with that every day, any hints? Thanks in advanced CI.-