I follow the maps faithfully but never download the kmz file. What am I missing?
You're not 'missing' anything as such, but they do allow you to follow the route more closely, view it from different angles, get more of a feel for the terrain etc. I use them on my blog and for Outreach work, obviously, but I think they're a fantastic resource for anyone following the mission. And if a UMSFer produces something so useful, in their own time, it's only fair that we support their efforts.