I use Debian’s full drive encryption and have for the last two years. The performance penalty for a 1.2GHz P3, Thinkpad X30 that mostly ran at 800 MHz, was not a problem. Suspend to ram also worked, though you should probably not do this or suspend to disk if your laptop is a matter of life and death to someone. This is practical privacy. If only my friends and family would use reasonable software and encrypt their email…

Do not trust hardware encryption, especially one that stores the password in BIOS. Hardware and software vendors that sell users out are more common than evil maids, who mostly exist in Microsoft sponsored FUD. You are in better hands with the free software community and can verify their work for yourself if you need to. The elusive Evil Maids would also have an easier time with non volatile bios memory than DRAM, though that may depend on the laptop build.

If information your is really so super sensitive, you should keep it on a well guarded server and only access it with a secure machine. SSH and networks are wonderful tools. Border guard kept a copy of your hard drive? Let them crack the empty container. If you get it back, wipe and reload. Be sure to have rsync your information to other secure locations. The rest of us can get along with full drive encryption.