Most people, in part because the marketing folks tell us so, believe that the addition of wireless to the HART standard is the most important part of the latest version. I beg to disagree.
The majority of new electronic field devices being installed today all have some form diagnostics capability and most of those also have some way of communicating their overall general health to another system that can make use of this information to improve overall plant reliability.
We have been working on a Web 2.0 Social Media enabled way for the process automation community to discuss, teach and learn about usability issues in process automation for some time. It is called the Process Automation Usability Project, and you can find it here.