Visio was never a good tool to diagram processes in BPMN. It was just shapes to connect them manually with arrows and that’s it. It was ridiculous in comparison with specialized tools like iGrafx. But the new Visio 2013 version is far much better than it was before. You can see it in action on this Youtube video:
You can add new objects to the flow by pointing on the shape and selecting next shape.
You can connect one shape to another by just grabbing an arrow and connecting to desired shape.
You can change options of the task to get loop, compansation or other. And you can decide that it is manual task or send-receive etc.
Unfortunately you can’t select option to handle error event on that task. You need to add intermediate event and place it on the task shape. It is really bad design.
You can’t export your diagram to BPEL so you can’t „run” this process anywhere. You can’t simulate neither.
Swimlines works quite nicely. If you put one on another they are merged like this:
As a summary. I can say, that it is not the best tool for BPMN diagrams, but it is usable and Visio is a „standard” app for diagramming in many organizations.