Agreed, this is my favorite too. And, after you encrypt your primary drive, you can either leave your Time Machine drive alone (which seems silly, but it's an option now, whereas before using FileVault created an encrypted disk image, which meant Time Machine could no longer backup changes-only, defeating the purpose of TM), or you can go into TM settings and encrypt your TM drive too.
You can also encrypt secondary disks on the command line. It all runs silently in the background until encryption is done.
You can also encrypt secondary disks on the command line. It all runs silently in the background until encryption is done.
There is a 20-30% disk performance hit (that I haven't noticed, on an SSD): http://www.anandtech.com/show/4485/back-to-the-mac-os-x-107-...