"... most of the advantages it has over physical / digital cash or credit disappears once you add such things. Once you have a ... physical device governments will get into the game and start regulating"
Not sure what you mean. By 'device' I didn't mean some special hardware developed by some special company, where the government can then regulate that industry. I just meant any computer. I'm saying that signing a transaction can be done offline on devices that are never connected to the Internet, such as an old laptop, or yes even a special device. There's no fundamental requirement to have the keys on your virus-ridden home PC at any time. This doesn't remove any of Bitcoin's advantages from what I can see.
And multi-signature transactions will allow for multi-factor authentication at a protocol level.
That's significantly worse from a user perspective than giving Amazon a credit card number to enable one click checkout or downloading a book from my kindle. It's true you could do anonymous transactions online, but while it's better than mailing people cash it's something of an edge case and I could also buy a Visa gift card and get the same sort of anonymity. Again, I like Bitcoin, but the problem IMO is how to make it both as convenient as a credit card and secure.
PS: Your also describing an adhock solution. As soon as you want to mass produce them to allow significant and convenient adoption you get into regulation issues. And by 'device' I am including just the software to manage your account from a cheap netbook.