I tell them I want to get paid X dollars in bitcoins, and they tell me how many bitcoins I should ask for and what address they should be sent to. Stripe then gives me the dollars I asked for (minus a small processing fee, of course).
How much is the fee? Is it a fixed amount or proportional to the transaction value? How does Stripe set the dollar denominated bitcoin price? One easy way to make a bitcoin payment look cheap is to offer a low fee but offer a slightly inflated exchange rate and take a profit out of the difference between the rate used for payment and the rate you can get in the market (exchanges or dealers). It's hard to compare the economic value of dollar denominated bitcoin payments (relative to credit cards) without knowing these details.