I agree with sinco about the cases of declined credit card payments. There are some cases where in the MICC cannot draw the payment on one's card. However, there are many ways to avoid this such as to check to the bank if the card can be used to Canada esp MICC for immigration processing (its better to be sure). Some banks requires specific time frame the card allowed to be credited and they are asking the country specifically. Some on the other hand, says no problem as long as it is online. Anyways, it always boils down to the policies of the bank. Also, in my opinion it is better if the bank has branch in Canada for greater chance of acceptability. In my case, I used my Barclays credit card.
Some other applicants actually used debit cards and their payments have been successful.
I have read also in some threads that some applicants who had problems with credit card payment had their file opened and just informed them usually via regular that they had this payment problem and they are required to send another payment which way it is. Some on the other hand, returned the whole applications. This happened also in some applicants with expired demand draft also. It seems like it is all in the hand of IO. Let's just hope they are so kind to understand the situation. =)
I guess whichever mode of payment, there is always certain degree of risk. The applicant hereby has to do his research.
Best of luck to all QSW applicants. To those still haven't sent their applications please hurry up since as of July 18, 2014 only 1,381 slots are available but be sure to double check all the documents for completion and don't forget the payment. =)