I have a DeLorme PN60. I find the PN60 quite easy to use. On the other hand, the Topo software is clunky and hard to use. I spent a couple of days reading the manual and going through help files before I had everything working together.
Once I figured everything out, I am quite satisfied with the entire package. The downloadable maps that you get with a DeLorme subscription are great.
I'm using Windows 7, through VMware Fusion on an iMac for what that's worth.