The tool is similar to any 3rd-party booking platform, allowing you to search for fares across multiple hotel and rental car chains, with an easy-to-use interface. It also has similar pro's and con's to any booking tool, like losing out on hotel rewards and potentially enduring worse customer service than if you were to book directly with an airline, with the upside of easier bargain-hunting and price comparisons.
If you're the type of traveler who isn't too concerned with hotel elite status or who doesn't mind booking through a 3rd-party app, the Capital One portal should be fine.