For the longest time, I recommended everyone start with KC. And KC has a lot of strengths, its simplicity being a major one.

IS Boxer has a wizard, which gets you up and running in less time then adding all of the windows initially in KC. You don't need any knowledge of warcraft macros to start, just drag each spell to a slot on the bar. If you put lightning bolts all on '1'. '1' will have every toon assist the leader and cast their lightning bolt.

The Repeater Mode vs Keymaps, as independent broadcast modes was a bit confusing coming from KC, at least initially. The graphical click buttons help quite a bit here.