As a small time merchant who also accepts BTC as payment, I've never sold any coin that has been transacted for goods/services (the number of transactions has not been great, so can absorb that), though it appears that most people feel that it is converted to FIAT immediately.
Perhaps that is because of the long down trend we've seen, but if it starts to trend upwards then perhaps some of those merchants will start to speculate a little with what they can afford to hold if they can without needing it for cashflow purposes. If that happens then that could put a fire under the price and it accelerates away causing another bubble. I imagine that there would also be a counter to that where people only spend in BTC what they have to which would stifle that growth to a degree, but people might be more comfortable spending gains as needed, and I can still envisage a scenario of decent growth being possible, possibly a runaway success even.
I'm incredibly optimistic about the success of bitcoin, but to put a price on it could be orders of magnitude out of actual behaviour.
The credit card transactions have a fee, and we have to wait 28 days for payment, and then it's only 90% of total transaction value (that includes things like shipping that must be paid weekly and we end up paying for the privilege of being the banker to the transaction processors), and the remaining 10% we have to wait 6 months for. Would we discount for BTC? Sure we would, but if it were popular we'd probably start having to convert at least some of it to FIAT, at least in the short term.