Re: Anybody use a persistent USB install for thier main/only Linux system?
I use Heron-an-a-stick regularly - an installation of 8.04.1 on a SanDisk 2GB Cruzer for use with on my work laptop.
The Cruzer was a U3 device. Had to de-U3 it with SanDisk's tool (requires a Windows machine).
Persistence was broken "out-of-the-box" (known issue, with fixes available).
Does not shutdown the file system cleanly. No breakage or corruption, just an unclean shutdown. I fsck the casper-rw partition on it when I connect it to my Ubuntu laptop, otherwise bootup gets slower.
It boots and works faster than CD, but still nowhere near as fast as an install to hard disk goes. I was able to install what software I needed, which wasn't much. Keep in mind that persistence has limits - the more files you modify out of the fixed set equals slower response and not everything is persistable (to coin a word).
My needs are different from what you stated. I just wanted to be able work on OOo docs, and have a means for keeping personal emails off the corporate radar (I use it with a 3G phone).
Keep in mind a persistent install has a very generic view of hardware, especially video. It's meant to be portable, so things like compiz aren't doable since the "advanced" (proprietary) drivers aren't available. Even should you manage to install NVidia, that's not going to work an a machine with ATI video, etc.
Main system: Dell 1420n - C2D T5250, 4GB RAM, 120GB SATA. Ubuntu 8.04.3.
Assorted VMs (via VBox). Favorites: Fedora, FreeBSD, Solaris.