The problem with all fiat currencies is they have no inherent value; it is all in the eye of the beholder. So what is an "appropriate" price is quite difficult to determine. Most currencies are driven by being effective monopolies wherever they are issued, so the market price remains somewhat stable. Even so, many professional economists have opined that the exchange rates even between major currencies are way too volatile.

This is, among other things, because there is a whole lot of loose money floating around that can easily jump between currencies. We are probably going to see a lot more of this in the Bitcoin world, which I expect has a lot more volatility ahead of it -- somewhat ironically in this case, as the increased liquidity promotes volatility, since it becomes an instrument of pure speculation that was previously too difficult for professional traders to deal in.

In any case, I also had the intuition around the $11-12 mark that bitcoin was a good investment, since the major hurdles around the security issues were probably ironed out, but didn't invest anything -- probably because deep down I'm a value investor and don't see a lot of value in driving speculation in something that doesn't have inherent value (despite the many interesting technical aspects to Bitcoin).