I would keep it, definitely. The BTC you eventually mine will be worth more than the USD you will get from a refund. I bet the people who canceled their 6/23 orders for singles in April, May, or June are banging their heads on a wall right now. The only reason I would want to cancel is if the BTC price dropped significantly (down to single digits).
Even BFL sock puppets are starting to put it rather bluntly. Nice to read it. In a ward, never purchase a product from BFL. If you want to make a BTC investment just buy BTC with your USD and hold them.