Dirac - worth activating?

Worth it to most.

Certainly worth it if it is free and only takes time.
Then you know for sure whether it is worth it, and can also opine on it.
Or if it is difficult, then someone may be able to assist you.

Does it adj beyond processor?, ie. For stereo listening via preamp?

Good topic for me, have to jump in.

I have the NAD C658 preamp, the free dirac version (up to 500hz) is included. I'm only using that freebie so far, and I only toggle on when playing vinyl. I used the included microphone on the 15ft cord btw to setup.

Why? Because there's a major boost in gain, and without it my Starkrimson amp doesn't have enough gain (combined with phono amp, NAD impedance, unkown other factors). 

BUT! the happy gain boost is ONLY when the 'analog bypass' is ON and the dirac profile I created is enabled. When streaming there's not much a gain difference, but there is a frequency/dirac difference (mainly bass is way flatter). I've thought about posting this oddity actually in a separate NAD / dirac post actually. 

Definitely worth trying.  I bought an Arcam SR-250 AV 2-channel receiver which comes with Dirac Live.  It required a bit of a learning curve but made a huge difference in a pair of Martin Logan speakers.  I was so impressed that I bought the Mini-DSP DDRC-24 for my main system when I was trying to integrate a pair of Legacy Focus speakers in a smallish room.  Again, a huge improvement but I ended up selling the speakers because of their size/weight.