Two (and a half) FileVault questions

And here they are (they should be simple to answer):
1) Can you turn FileVault off after has been turned on?
If yes, will the filesystem become unencrypted?
1') How much of a performance hit does it entail? (After the initial phase).

2) If FileVault is on, and I use scp from terminal to send a file to another computer (a UNIX machine), will it be encrypted? Will I be able to read it on the UNIX machine?
The reason is that I have a cron job that syncs my "research directory" with the department server (UNIX) using rsync. I need the files on the remote UNIX to be unencrypted and readable when I log there.

For some (psychological) reason I am wary in using FileVault, primarily because I don't have that much of sensitive info to begin with, but also because I am not sure whether the process is completely reversible and how really transparent it is.