Private currencies could become a reality, oh wait e-gold? liberty dollar, bitcoin, etc... what do they all have in common? The government will somehow find a BS reason to shut it down because they hate competition. All your reasons are BS plain and simple.
Confidence in a currency has to be built and can be destroyed instantly. A government can ruin the confidence in its own currency the same way (read: US dollar).
We haven't had a gold standard at all since the 70s dude, and even then it was kind of a BS system. Hence one of the major reasons for the out of control spending we have going on right now.
If they told you US currency was backed by anything other than faith someone lied to you.