Hi John!
I'm deep into an unexpected/unwanted kitchen remodel, have nearly concluded the cabinetmaking and am moving on to the electrical end at the moment, so must be briefer at the moment than usual until later.
I have a Garmin Oregon 400T, and have found this resource to be especially helpful:
http://garminoregon.wikispaces.com/I do run both an 8GB card and a 4GB card and load maps and routes on each (I already had two cards, so I use them; would be more useful to have one, as micro SD cards are tiny and subject to loss when changing in the field. As it is, I keep all North American City maps and National Parks maps on one, while I keep all of Europe on the other, along with the BENELUX bike paths and some individual recreational maps for BE, NL, and FR as well. The spare space on each holds either my tracks or my custom map uploads and my Garmin satellite photo overlays).
Are you using MapSource or BaseCamp as the intermediary software to transfer your maps? I've run into some problems if I do otherwise.
I wish technology was as easy as riding my Thorn!
<nods> Agreed. Garmin's interface is not as consistent or intuitive sometimes as one might wish.
Best,
Dan.