I have been impressed with it, having played with the multichannel demo from Dirac. Makes the cheap-o speakers in my HT room sound pretty decent IMHO. Mini-DSP also make a couple boxes that use Dirac.
Might be worth ordering a UMK-1 and putting the demo on your Mac-mini to see what it can do. The UMK-1 can also be used with most measurement software so it should not be a loss if you ever plan on doing computer based measurements.
Really wish I had the coin for a Datasat RS20i.