Bamboo integrates very nicely with the rest of the Atlassian Suite of products such as FishEye and Crucible. It's also very easy to use. I am predominately a developer and not a scrum master or maintainer of the Atlassian projects in my company's role. However, I can easily go into the Bamboo console and start off a build manually if I need to.
While it can be a free product, it is only free for minimal functionality. After that there is a charge.
There is a lot more that Bamboo can offer than what I described in my review. I would recommend reading more into the documentation provided by Atlassian to get the most out of the product.
If you don't know if you would find Bamboo useful, they do have a free trial version that allows you try some of the features before signing up for a paid tier.
Bamboo allows us to set up scheduled builds that occur at a particular time in the middle of the night (as to not disturb any developers that are testing against a particular server). This has automated the build process and saved us a lot of time when testing new builds. We get detailed logs and information when a particular build fails.