Is MIR worth it? I questioned the same thing.
My first decent reverb unit was a TC Electronic M3000, that cost more than twice than MIR, I then moved to Powercore and VSS3, that also cost twice the cost of MIR. Last year I moved to Vienna Suite, which cost a lot less than VSS3, and that sounded so much better.
I had carefully mixed with multiple instances of Vienna Convolution reverb, panned everything where it should be, and was carefull to get the tone and levels right, and it sounded really good, I was really pleased with the result. I then downloaded the trial version of MIR Pro, put the same score through MIR, and muted the Vienna convolution reverb. The difference really surprised me, it all sounded so much more believably real.
So yes, MIR is worth the money, I just hope my demo license doesn't run out before my license arrives ! And on the demo license, I only have access to one position in one room, so the full version is going to be even better.