The reason why BTCs are not much an usable currency for a whole economy is that they are a deflationary currency like gold, meaning the more time passes the less new BTC are created till the end with no creation at all. This means they will always more interesting to be stockpiled then spent. Also they can't decrease nor increase "as needed" the BTC base, meaning that if you are short of natural resources you can't reduce their usage tightening the number of circulating money.
The idea behind BTC is very valid, but they can be more like the old ECU or CFA/CFP not money you normally use for day to day stuff.