My c320 arrived today!
I put in a 2GB SD card and loaded up ALL of the North America map info onto it - that took the better part of 2 hours.
Did some basic configurations in the setup menus and then let it try to tell me how to drive home. It recalculated a couple of times (I drove my normal commute route) and once thought I was on a parallel side road (due to recent changes in the main street's layout). Other than that it was really fun.
This independent review says the screen backlighting is a problem in daylight (not bright enough), but compared to others in that price range there isn't much room for complaint. It's certainly bright enough in the evening hours.
Another complaint is the lack of verbal announcement of the intersection names. Meh- I can afford a glance down to read the name.
My housemate was going out to dinner so I tossed it to him (well, not really) with about a minute of introduction. He had no problems and ran it for both legs of his journey. Now he's thinking about getting one.
Truly a marvel- and a great price.
Of course, next year a navigator GPS will be the size of a wristwatch, cost $50, and be compatible with the OS in my flying car... but for today the c320 is a cool widget.