The winning flavour in the 2008 one was Builders Breakfast, which frankly was god awful. It had a nasty eggy taste. It got pulled off the shelves after about a year. I still remember the lush fish and chips and onion bhaji flavours. Why one of them didn't win I'll never know.
The winner of that competion got £50,000 and 1% of all future sales of their flavour. This time its better since the winner just gets a one time payment of £1 mill. So even if Walkers makes the winning flavour taste nasty and it bombs, you still get the cash anyway.