if the user is offline for extended periods or does not have ready access to AGOL or Portal, exporting to shape file and kmz would allow the user to work with the collected data in the field and share with other GIS apps.
The whole point of the sync functionality is so that you don't end up with all the different versions of the data floating around on local computers, confusing users as to which one they should be using or they end up using an old version of the data because that is the one they have on their computer. This idea completely undermines that.
I agree with Clark Langridge if you operate in an environment were you are connected most of the time.
That unfortunately is not yet the case for some remote communities.
Then I would suggest using ArcPad, because it does exactly what you are looking for. http://www.esri.com/software/arcgis/arcpad
ArcPad is no where near as easy to use as Collector, however, and doesn't run on as many ubiquitous devices as Collector. I'm with you, Mr. Achilles, and voted this up. My customer loves the ease of use of Collector, and it would be a nice feature if they could optionally pull off points, polys, pics, etc. while in the field. If anything, it is also a nice backup feature should something go awry with the sync process or device (see Backups for Collector ).
Retrieving data ...