Once I found out the the Nexus 7 had USB OTG, the lack of an on-board card slot was absolutely
not an issue. There is a nice video demonstrating how that works here:
http://www.xperiablog.net/2012/03/09...strated-video/.
I routinely carry a 500 GB portable drive with me, so it's not anything new or onerous to use that sort of thing, if I ever need it.