Windows Phone only uses MS Points for in-app purchases. Apps are listed in dollar amounts, and charges go right to your credit card, not to your point total.
In-app purchases are MS Points, which I didn't realize as I don't have any programs that do in-app purchases, I don't think.
Nice to see the system go. I get the ease of currency exchange on the back end, but this is harder for the consumer, not easier, and it's like stupid tokens at your local arcade. No one liked that and everyone knew it was designed to screw them. Especially MSPoints, with the 4:5 conversion rate. 800 points = $10? Stupid.