This tool significantly simplifies the process of adding buttons to the ribbon by providing - as the name suggests - a graphical user interface for interacting with the CRM ribbon.
This tool doesn't completely eliminate the requirement of having to understand the various ribbon components and how to go about implementing Actions, Display and Enable Rules. However one of the biggest benefits is that it does all the legwork as far as formatting the underlying XML which can be a little tricky when trying to manually configure this option.
Simple requirements - such as adding a URL link to the ribbon - can indeed be performed entirely using this tool. However more complex requirements will still require manual intervention such as writing the jscript function that the Action, Enable or Display rule may call.
In addition to this, the author of this tool also mentions that it does not cover all configuration scenarios that the ribbon XML offers and lists a number of cases that are not supported on the codeplex home page. But even in those cases, this tool provides an excellent starting point by allowing for the basic XML structure to be created.
For example, I wanted to configure the "Phone Call" button such that it appears on the MainTab of a form. To do so, I pretty much copied the definition from the "Add Phone" under the Related tab.
Before this feature can work it is necessary to also pass a parameter to the jscript function (this can be viewed by downloading the application ribbon definitions) which can not be performed currently using this tool. At this point, all that is necessary is to export the entity ribbon in question, manually configure the XML to pass the parameter, and then re-import the updated application ribbon XML.
In short, I was able to use XML visual editor to configure 90% of the ribbon component and not have to worry too much about making sure that the XML structure respected the ribbon schema definition. The remaining 10% needed be configured manually by just updating the relevant parts within the already formatted XML structure. Very useful indeed.