WPF Ribbons: Comparison of Microsoft, DevExpress or Fluent?

Fluent Ribbon here! The Microsoft one lacks good support

Update:

Please vote on the Microsoft UserVoice site about the buggy Ribbon control:

https://visualstudio.uservoice.com/forums/121579-visual-studio-ide

Fluent Ribbon is I believe a great choice if you're looking to customize the styling of your ribbon. For example, Microsoft's Ribbon control has had theme options removed and is now only shipped with a single theme.

From my experience, Fluent Ribbon is not so great at design time building in Visual Studio, but in all other areas is superb. It is Open Source so can be customised to your needs and, coupled with MahApps Metro package, you can have complete Metro-styled applications with ease. Below is a screenshot of a sample application made with Fluent.Ribbon, using its 'Office 2013' theme.

Other commercial Ribbons are available and offer more features (such as three-state visibility, as show below in a screenshot from Outlook 2013)

I would advise making a list of all the features you require from the Ribbon control before deciding which one to use and whether a paid commercial Ribbon makes sense for your scenario. In your case, you already have access to DevExpress, so perhaps that may be your best choice.

I believe one of the most used is the Microsoft one.