I disagree with this statement.
I've been using FDE on every laptop I have owned since 2007 - Windows, OS X and Ubuntu. The laptop I am working off of right now is a 2011 MBP with a solid state drive, and it is still fast enough to run VMs, Photoshop, Lightroom, video editing, and anything else that is considered CPU, hard drive and graphically intensive. Even though it is 4 years old with FDE, I have no reason to replace it.
In many configuration, the performance impact is negligible.
http://osxdaily.com/2011/08/10/filev...mac-os-x-lion/
http://www.anandtech.com/show/4485/b...lion-review/18
http://apple.stackexchange.com/quest...cess-on-an-ssd
Especially in the past 3-4 years, FDE performance has improved substantially.