I don't own one, but I demoed it for about 45 minutes. I really like T-Rex pedals man, they're some of the absolute best ou can get. I have 2 Dr.Swamp pedals (I bought the 2nd for backup).
The Bloody Mary is a cool pedal. I was comparing it to
a Krank Distortus Maximus. Having a 3 band EQ on your distortion pedal is great. To me the Bloody Mary pedal sounded kind of a like a saturated Marshall type of distortion. I was more impressed with the midrange lead sounds than with the scooped sounds. I'm not into scooping all the mids anyway so maybe I just didn't dial it in right for that kind of thing.
Even for heavy grind, I still like to have some mids in there. I'm sure this pedal could do it. The sound is kind of hard to describe, maybe a Marshall-meets-Fryette type sound.
T-Rex pedals all have excellent definition, sound and play like tube amps, and have a super response. Not too immediate to where it's like playing a solid state amp or something, just a really awesome pick response that feels natural like a tube amp. One thing about T-Rex pedals is they all seem to blend really well with whatever amp you're playing.
After comparing the Bloody Mary and Distortus Maximus, I came to the conclusion that the Bloody Mary is definitely better at the lower gain thing. It also has more distortion on tap than the Distortus Maximus. I think both pedals are awesome, but the Distortus Maximus pretty much just sounds like a Krank amp. The Bloody Mary can do more.
Hope this helps some.