I just discovered that when you import a conference proceeding record from RefWorks to Zotero (bulk RIS import) it puts the conference date from RefWorks in the Date Accessed field in Zotero.  Which means we lose conference date info.  I've been intentionally leaving the year blank for conference presentations/posters that aren't in published proceedings, so I foresee a lot of data cleanup in my future.

UPDATE:

I think this is an issue with RefWorks use of RIS tags.

Refworks puts conference date in RIS Y2 (which is "Access Date") I think I can fix this by replacing Y2 with DA in the conference records before importing them. 

Not seeing a way to get the conference location to be imported, though?  Refworks puts it in RIS CY (Place of publication), but no data are importing for that field for the conference records =(