I used to use a Garmin Venture for quick and handy area calculation.  Worked well, no major complaints.  The lack of memory was only a problem when trying to load maps into the unit for large areas that included major cities, which isn't a problem around here. 

 I've since upgraded to a Garmin Legend Cx with a 64 meg card and colour screen.  Lots more memory for map storage if I need it for travelling to major cities, but I like the colour screen better and the battery life is much better than my old Venture.  Rated for something like 30 hours on a set of batteries if you put it on battery saver and don't run the backlight.  It lives on my belt year around, just in case.  You never know when someone wants a price quote or is interested in selling "the back 40" that turns into "the back 25" after you walk around it. 

 The new Magellans do area calc too, but they got into that after I bought my first Garmin so I didn't want to get into new mapping software, etc so I haven't tried one of those yet.

  Oh, I had one of the first Magellans with a colour screen that had an internal compass.  Loved the compass for finding waypoints when I was close but hated the screen (barely visibly in daylight) so I took it back after less than a week.  For area calc and basic navigation I don't think you'll need the extra compass.  It only comes in handy if you stop moving and want to know the direction if you spin around.  Good for geocaching but I haven't found it useful for finding farming waypoints again.  If I get close enough to need a stationary compass in my GPS I can usually see the rock, bug infestation, or whatever else it was that I was marking. 

  I usually use Fugawi to import my Garmin tracks, waypoints, etc for backup and working with scanned maps and aerial/satellite photography.  Works well for me, but I don't have OziExplorer or whatever to compare it to.