I originally had a Garmin 92 - very basic, like the Garmin III
I then added Memory Map and a GPS sleeve to my IPAQ - I have a different view about this - it's fantastic for route planning, but I found it is not user friendly in the cockpit - the display is not as clear in bright light, you have to use a stylus or leave finger prints to make changes etc. You certainly don't want to change your route plan mid flight.
I have recently bought a Lowrance Airmap 500. About the same size as the Garmin III it comes with all the accessories, so the price is the actual price - less than £400. Bigger display and lots more features. Easy to use, easy to program - uses 2 AA batteries that last forever and although it comes with an external aerial it is happy with the inbuilt aerial on the yoke mount on a PA28. Apart from the map display (which you can add ground features to) it has a decent CDI display and a unique airfield approach view which shows the runways orientated to the way you are approaching the field.
It all depends on how you plan to use it and what you expect of it in the end - we're all different after all!