Credit cards would be awesome, but its really tough to use a payment system that can be reversed (credit cards) to purchase bitcoins. Obviously the bitcoin transactions cannot be reversed without the recipient's consent.
I know a lot of people here like this about bitcoins, but I think it's probably the single biggest obstacle to getting the general population to adopt them. At the very least, people would need a system that can handle the tougher parts of spending bitcoins for them. It doesn't matter how much better the system is if another one is much much easier.