Fantasy Insider is designed as a tool to help you make your own lineups. While we publish an optimal lineup, we don't play that lineup in each type of contest. Many of our subscribers do, and do so profitably, but the more users that enter an identical lineup the lower the profit margin. Our subscribers have won over $250,000 in prize money since we launched the site, mostly using small variations on our optimal lineups. You can read some of my summaries here  , and one of our subscribers stories here.
In many ways, Fantasy Insider is analogous to an advanced Horse Racing form guide. We display a number of the best selections for each game, and we give you the tools to delve into the combinations of lineups you can put together to enter into a given contest.
If you use the projections, we're confident in the long-run you will be a profitable player. If you combine them with your own intuition and research, your profitability will increase. Taking a long-term view is essential in DFS, where the weekly variance can be high, so you should make sure you're not entering more than a small percentage of your total bankroll each week.
In the end though, this is gambling and it is not possible to guarantee returns. You should only ever bet with money you can afford to lose.