I have finally (!!) managed to experiment with DIRAC today which I've been wanting to do for a long, long time.
I ran measurements with UMIK and ran the filters through JRiver and fed the LCPM signals into my Chord Mojo DAC and then into my Arcam C31 pre.
My thoughts were that it was not as big a change as I was expecting. I have very poor room acoustics and it did improve on these somewhat. Imaging felt more tightly focused but less expansive. In default mode (i.e. correcting 20Hz-20kHz) it trimmed far too much off at high frequencies and completely robbed the sound of 'air' and cymbals took on a muted quality and lost their radiance.
I limited the upper frequency bound of the correction to 1kHz and experienced better results - this retained the 'air' of the recording whilst tightening up everything below this frequency.
Having listened extensively I cannot say it was substantially better than listening without an EQ in the chain - only different.
However, I was very surprised to find the EQ is extremely transparent - I cannot hear any real distortions being added into the signal, which is a big, big improvement on Audyssey that gave fantastic measured results but ruined subjective listening.
Having listened I can now genuinely say it isn't for me, but I would actually recommend it for those who need an EQ, especially in surround.