The first time I did a check for them, there was an issue with my paypal and it took some back and forth to get paid. I had entered my paypal email when I signed up, but for some reason it hadn't saved and they had to enter it manually. I used the contact form on the site to alert them to the problem. It took a few emails back and forth to sort it out and they were kind of slow to answer.
However, I have done about 8 more shops since then for them and have always been paid promptly. Looking back at my payment history, the last assignment I did with them was on July 22 and I was paid on August 19th, so it was less than a month.
I agree that it is better for you to give the MSC an email that is linked to your paypal account to avoid any problems with payments. Many companies stipulate this.