I'll be keeping my Astro 220 for abit longer.... I was hoping for the BIGGER screen. I'm getting older and its getting harder to see. I like the swapping your buddys dog info over a radio signal and a couple other very minor options. Overall I think the 320 is just a software upgrade with a new case. A whole 25 cents to manufacture...
http://www.gundogsupply.com/garmin-astro-320-review.html