Every Sunday
I use DM's familiar EVERY Sunday during my game. The combat board alone is worth it but having the monsters, spells, skills, feats, and adventure information sitting in a handy little tree outline format is friggin' brilliant.
When a combat breaks out, you just drag encounters from the tree outline to the combat board and, voila, all of your monsters are sitting on the board, initiative rolled and sorted in proper order.
There are other features but you really have to use it to appreciate it. If you use a laptop at the game, this thing is a godsend. I couldn't run my games half as fast without it.
Sam