First things first, this mic is extremely well built. Very solid Audix build quality. The body is weighty, the XLR connection doesn't budge and the grille is very strong.
The clarity is pretty good, but being a hyper-cardioid mic with the capsule very near the grille, you tend to come across a LOT of proximity effect.
This mic sounds great once high passed and processed, but won't sound as good as other stage dynamics straight out of the box.
Good for vocalists with good mic technique, but doesn't sound good on vocalists who swerve on and off axis. The level and tonal change is very dramatic unless axis/distance remain very consistent.
Off axis rejection is very very good and gain before feedback is the best I've seen. Very useful indeed on loud stages.
Dave Rat (live engineer for Blink 182 etc.) has a great video demonstrating the off axis rejection of this mic here >>> >
Overall, I would only recommend using this mic if you are/you are working with a vocalist who understands the principle of mic polarity and proximity effect and is fighting against high stage volumes.
In most cases, you will get better results from an SM58 (less proximity effect and less off axis colouration), but if you are woking with an experienced stage singer with good mic technique on a loud stage - no other mic will do the job better than an Audix OM7.