This morning I set about updating my maps, but because I wasn't quite sure where my Zumo was I just had Garmin Express do it for "Computer Only", about a three hour download on my rural network connection. It completed successfully, and in the meantime I found the device. I plugged it in and set Garmin Express to updating it ... only to be dismayed to see it going through another 3 hour download because it won't use the data that is already on my computer. I'd hope it would be much smarter about this.
I guess maybe in BaseCamp I could have used "Send Maps to Device", yes? Still, it'd be cool for Garmin Express to do it sensibly.