I have bought several things on etsy since direct checkout and I am not sure what you mean by the default payment. When I checkout I immediatly see the option for both paypal and credit card. I have not actually paid by DC, I prefer my paypal since I have funds in there, I don't need to fill out all my CC info...its just easier to subtract out of my PP account.
I have DC in my shop and about 1/2 of my customers use it. I think it's great. I was nervous about the wait period and no credit until shipped, but once you get a little money built up, I don't even notice it. Plus if you need funds sooner, you can request it...there is always immediate withdraw from paypal too.
I don't know if it has boosted my sales...could be coincidence, but I don't want to turn it off thats for sure...things are going well.