The multi-channel PC version of Dirac 2 isn't yet available so I've only heard the stereo version and why i didn't comment. I expect multi-channel to be out soon. I can believe that with multi-channel the improvement is incremental because what was done with phase was aimed at stereo reproduction. Also, subjective opinions can vary greatly.
I feel the improvements with stereo imaging can be great depending upon speakers and one's subjective opinion. In my set-up with Theta Gen VIIIs, ATI Signature amp, to be supplemented with Mcintosh MC611 monoblocks asap, and Mcintosh XR200 speakers the improvement is there but not huge. However, I mainly run Dirac below 300Hz because I am happy with the sound that way for stereo.
Another friend/client has a different set-up. I use the /client because he did pay me to build bass traps and acoustical treatments for his room though the pay wasn't really what a professional would be paid. I sometimes toy and experiment with turning my hobby into a business. His set-up consist of PS Audio BHK preamp and PS Audio BHK monoblocks with custom built speakers and ribbon drivers. At his place, running Dirac 1 full range killed his stereo imaging. The sound stage depth from front to back was severely impacted. He refused to use Dirac 1 primarily because of that. With Dirac 2, the stereo imaging is excellent. With Dirac 1, he was so "turned off," that he would not use it even with it correction below 300 Hz. I know this is blasphemy, not using room correction, in some circles. However this guy is a former professional jazz musician. He is able to analyze a recording and really dissect everything that is happening in that recording from playing styles of the musicians to the compression or lack of in the recording. He knows what he likes.
As we all know, part of what make the sound field of a multi-channels set up seamless is when you not distracted by channels that don't "match." We match channel levels to try to aid with this. Matching levels only get you so far, especially if all speakers are not identical and even then, they aren't in the same positions. Running a full range correction on all speakers and more closely matching the sonic signature of each speaker, greatly assist with the seamlessness of the presentation. I think it's essential for a home theater set-up.
For me the new Dirac 2 is important because it crosses a threshold where some who would not use a full range correction may be willing to now do so. The greater benefit for Theta is with the multiple presents, you don't have to compromise by running a below 300Hz correction even with multi-channel because you only had one option and stereo was your priority. Some are still not going to like room correction because "processed" sound to them is a greater evil than using room treatments and no room correction. I am not in that camp but don't fully commit to full range correction either for music.
A long time ago, when I purchase my first solid retractable screen, I noticed that with it down the sound changed. I played music, lowered the screen and heard the sound change. So when I run Dirac 2 multi-channel and purchase another retractable AT screen, I can have presets for when it's down or up, a preset for stereo, and a preset for multi-channel.
Never become so involved with something that it blinds you.