I'd dispute the assertion that transaction times are slow, given that it probably takes at least 24 hours, usually more, for an interbank transfer to make its way through our decrepit clearinghouse system.
I generally agree with this. However, I've heard concern that Bitcoin may be too slow for in-person purchases.
The counter-argument is usually that credit cards allow charge-backs for at least up to 30 days. It may be that the current credit card system only works because merchants trust that credit card companies will reasonably protect them from fraud. I'm not 100% convinced one way or the other, any insight?