I have dealt with MVP on and off for a few years and they have been reliable for payouts so I wouldn't worry from that perspective.
If you started thinking about doing more ongoing business with them, some caution is required. Make sure you read and fully understand their payout conditions. They're not particularly friendly when you get into higher dollar amounts.
I have also found that you can't really trust what their telephone reps tell you. The obvious solution is to get everything in writing but both MVP and V-Wager are terrible at answering e-mail.
My overall opinion: congratulations on winning the contest. Good stuff! As for having a long-term relationship with them, there are many better books.