Andrew, running a Property Export like this should have almost no performance impact, mainly because we're requesting a very small set of properties on only a few folders at a time. A Content Report will put a slightly higher load on the server, since it actually looks through the items in the folder.
John, yes you can do that using Custom Bulk Operation from the Tools menu. Just go to Tools -> Custom Bulk Operation. Leave the Base set to Mailboxes. In the Overall Filter you can filter by any MAPI property by specifying its hex value. For instance, if you only wanted to do folders named "Calendar", you could filter on PR_DISPLAY_NAME like so:
(&(0x3001001E=Calendar))
If you wanted to do any folders where the default message class is appointment, you could filter on PR_CONTAINER_CLASS:
(&(0x3613001E=IPF.Appointment))
Once you've determined your Overall Filter, hit Add to add a new operation. Choose "Other Folder Properties" and click OK. Change the Action to "Export", specify an export file, and then choose each Property you want to export from the dropdown list and hit Add. Click OK when you're done building the list of properties, and then click OK in the Custom Bulk Operation window when you're ready to run it.
You can find some other examples of using Custom Bulk Operation in a couple of previous blog postings. I described how to export permissions on all public folder calendars here: http://msexchangeteam.com/archive/2007/02/16/435378.aspx. I describe how to set permissions on all mailbox Calendar folders for languages where it shows as something other than "Calendar" here: http://msexchangeteam.com/archive/2006/06/13/427944.aspx.