I've been running BT5[r1] as a "disposable OS" almost every day on a laptop for months now, booting up from a CD. Great stuff. Boot up, do your dirty work, shut down, and all the evidence is gone.
A few weeks back I installed the BT5 ISO to a USB stick with UNetbootin and tossed the CD forever. Excellent perfomance. Now it boots up fast and quiet. But there's one tiny issue: it still thinks it's a CD so I have to run my apt-get script every time to get the utilities I can't live without. I thought I could get the same performance by installing the OS itself onto stick, so I bought a cheap 16G thumb drive and tried it out.
Boy was I wrong!
I installed using the defaults and booted the stick up. It was dog shit slow—slower than using a CD at times—but it was still usable. Disappointing, but usable.
After a few days of this I did some research to see what I did wrong. And I found that it's not a good idea to install onto USB using the ext4 filesystem (the default). Either ext2 or UVFAT (formerly known as UMSDOS) is recommended, and UVFAT doesn't work on 2.6 kernels.
I reinstalled to ext2 and booted the stick up. It didn't boot because it switched from sdc during installation to sdb at boot time. Editing grub.cfg took care of that, but after rebooting it was still dog shit slow. Not sure why that wasn't a problem with ext4.
So I decided to simplify things. Instead of messing around with multiple partitions I made one big one and used a swap file instead of a swap partition. This offered a mild improvement but it's still a dog.
There must be a better way.
Oh and by the way... if you've ever installed BT5 to anything, you will find that the last 1% of "almost finished copying files" does indeed take for-fucking-ever. With the ext4 install, it took twenty minutes. With the ext2 install, it took from one hour to "screw it I'll check it in the morning". So be patient. And don't use a CD. Install it from USB.