I guess it depends what you want from a GPS.

My own needs would dictate a handheld with Macintosh compatibility
that can take uploads from chips.

I wouldn't really need it for navigation, as I almost never visit a
city where I'd need one (Wellington or Auckland), but more for getting
gridreferences for fossil localities (lat-long format sucks). For this
I'd need both the universal transverse mercator grid and the New
Zealand grid... meaning I'd need a $400-or-so purchase of map
software, which equals the purchase cost of a top-of-the-line Garmin
GPSMAP60. That doesn't make sense to me, hence my refusal to buy one.
And if I wanted to use it on a visit to say Australia, Canada or the
US I'd have to buy the software for those countries in addition.

The screen on these is far too small for car navigation... you can't
mess with magnification etc on the go, you'll have an accident. I
guess you COULD get an electronics whiz to make an interface to
connect the thing to a big dash-mounted monitor (Apple 24"?), but what
would that cost?