Indeed, it is a myth. From the Microsoft Exchange Team Blog:
We work with a number of Line of Business Applications (LoB) that develop a good part of the collaborative features on top of Exchange Public Folders.
In our experience trying to migrate some of these LoB application collaborative features over to either the Companyweb site or a dedicated SharePoint site on SBS we have seen some very strange behaviours in the apps once resident in SharePoint.
In our experience, there is a functionality in the Public Folder setup that does not seem to be there in SharePoint.
So, when a LoB requires Public Folders, we set up the prerequisites in Exchange and then install and configure the LoB app.
The Guidance post above has a good grid to provide us some direction in the decision making process between Public Folders or a SharePoint list or library.
Microsoft Small Business Specialists
Co-Author: SBS 2008 Blueprint Book