Well the basic fact is that ALL fiat currencies are printed to such an extent that there is always inflation. With bitcoin the currency can actually increase in value. If bitcoin were a fiat currency this would NEVER happen. Just imagine going to mtgox. The first day: $1.00/bitcoin, the next day $.95/bitcoin, the following day $.90/bitcoin etc etc etc. When you hold fiat currency, this is what is happening to your wealth. The wealth is being transferred to those who print the money.

With bitcoin the price can actually go up which is amazing for a currency. Thats something that only tangible assets do and that is so because those assets are inherently limited to something.

The simple fact that bitcoin has a limited supply, and controlled growth rate makes it 1000x better than fiat.

Also even if bitcoin doesn't go mainstream, the people who hold bitcoin are much better off since they can easily convert their btc to fiat and vice versa. We all have to keep some amount of cash reserves on hand to pay bills. Normally this would be saved in fiat, which always loses its value. However, with bitcoin you can now transfer some of those cash reserves into bitcoin so atleast it maintains its value.