IMHO there is one killer feature for decentralised payment systems: it allows people who can not get a bank account with reasonable terms to make monetary transfers. People who are born into rich first world countries don't realise how difficult it can be. In many places in the world you can not get a bank account unless you have an address. You can not rent a place unless you can transfer money. You are stuck. Even when I first moved to the UK, there were many flats I couldn't get because 1) my bank account in Japan refused to let me transfer money internationally (because I'm wasn't a permanent resident of Japan) 2) I couldn't get a bank account in the UK without a permanent UK address 3) Most letting agencies wouldn't take cash. I eventually had to make a 5 month deposit (think London prices!!!) to get someone to take cash so I could get a bank account.

There are lots of these kinds of catch 22s in the world and they are much, much, much worse in developing countries that have a large disparity between haves and have-nots. There are places where you are basically locked out of commerce of anything larger than pocket money -- because that's the way the large institutions want it. If they allow you to do business as all, it comes with a really hefty price tag.

The potential Bitcoin for me has always been one of 2 things: 1) a potentially convenient way to do online shopping 2) a way to enable commerce for the poor or disadvantaged. For years and years, I was unable to to get a credit card in Japan because they were unavailable to people without permanent residence status. Even now, the only bank that agreed to give me a business account for my consulting company refuses to allow the business to have a credit card. I can not buy any business related supplies on credit. I can not make online purchases for my business in most cases. This is insanity, but there are no banks who care where I live and they have a monopoly.

This is the advantage of something like Bitcoin. It breaks the monopoly of the banks. Of course, that comes with a whole raft of problems, but it really is frustrating when people in privileged positions just refuse to put the effort into seeing that their privilege doesn't extend to everyone in the world.

Edit: I should actually add that patio11 does actually understand the banking difficulties in Japan, and has written a bit about it before ;-)