I have been looking at Microsoft Visio 2010 and I would recommend it to anyone seeking a simple process modeling requirements tool. Ultimately, when your 'requirements' phase in process modeling is complete, the business analysts must move away from Visio and into the business process management suite.
There are many, many users of Visio who are 'process focused'. Moreover, there has been a significant investment in process modeling using Visio. When teams, who have not used an execution-oriented framework such as PMF, move these models into execution there will be issues. Visio 2010 Premium will help a bit by doing a very competent job at supporting early (learning and requirements) efforts in process modeling. The 'check diagram' function checks the proper syntax of the BPMN shapes. For instance in the diagram below, there are two errors: a message is flowing the wrong way and there is a 'hanging' activity.
After you correct the issues the errors disappear.
Casewise, Orbis and others provide Visio 'bridges'. Yet, all these will change when other vendors will seek to capitalize on Visio 2010's new BPMN features. This tool also supports moving process onto SharePoint 2010. Overall, I commend the Microsoft Visio BPMN team for their efforts.