spin05,
No experience with Garmin's Hunt Maps. However, I just wanted to pass along that Birdseye imagery will overlay with the OnXmaps. The overlay will still allow you to see all markings from the OnXmap. To verify I was not screwed up, I turned on my GPS and enabled a Birdseye image. I was able to see the Birdseye and all topo lines and boundaries through the image...ect.