I 'grew up' with UTM and prefer it. Problem is most geocaching and most run of the mill guidebooks run off Lat/Long.

While I prefer UTM, I am being forced by convenience to use Lat/Long system.

On top of this, maps come in so many different scales now that it's almost impossible to find a map at the last minute or with trail detail that matches the scales on my UTM card or whats on the base of my compasses.