I use it. It has some pretty cool capabilities. It has firefox installed on it, plus i installed some apps from
www.portableapps.com. I run an entire Apache/PHP/MySQL/Perl webserver from it. It also has a decent website password deal that generates passwords for you and keeps them encrypted.
As far as invulnerability... if you ask me, if it's connected it's vulnerable, but from what I can tell, it keeps the logon stuff separate from the encrypted files, so it would take some time to crack, plus it uses a fairly robust encryption alg for the logon password.
I don't consider my self a security expert by any means, but this is what I know...
brute force is damn near impossible unless you have a program that guarantees password cracking in less than 10 tries, if you type your password in wrong 10 times it self destructs. Not sure if that means permanently or not, but it keeps a hackers options limited.
if you want any more info, PM me.