Continental One Wold
Over the years our family has earned free airfare, hotel stays, food and upgrades, so I know that these programs do work.
We have been on international trips and believe me those free breakfasts, sodas, snacks really help out a family of 4. We love the Hyatt with it's Regency Club level and Hilton Honors. These programs have really shown through.
The only downfall is when the points expire.
With 911 pre Deltas bankruptcy, we noticed that all the credit card points/double dipped, all of a sudden became worth only half their value. Quite disappointing.
For the most part, I encourage you to join them! There are many websites dedicated to all these programs.