Take it.
My course director's definition of dive training goes something like this:
OW: I'm breathing, I'm alive. I'm breathing. I'm alive.
AOW: I'm breathing, I'm alive. I'm breathing. LOOK! A Fish!
Rescue: I'm breathing, I'm alive. Pretty fishes. Wow, I have a buddy!
I chose to take the divemaster course, not so I could teach or assist classes. I decided to take it so that I would have the very deep knowledge of how and why diving works as well as get my diving skills extremely dialed in.
The material in OW is thin, but it's intended to be basic.
AOW's material is nearly non-existent. It's more of a way to wet your whiskers on options.
Rescue class brings you back to learning stuff. It rounds out the basic diver training.
Divemaster takes the time to get into the science and theory of diving as well as make you perfect your basic skills learned in your OW class.
I strongly recommend rescue to any diver. I would only recommend DM if you love knowledge and want to hone your basic diving skills (or want to teach).
