I went into the performance with several cameras and two primary lenses. I started out shooting with the Canon 5Dmk2 and the Zeiss 85. Then I switched to the 50mm Zeiss on the 5Dmk2 and put the 85mm on the Canon 1Dmk2n, just for safe keeping. Big mistake. The first time I pulled the 1D+85 combo to my eye and clicked I was hooked and shot most of the evening with that combo. Why? Great focusing acuity, lightening fast system response and the perfect ergonomics.
The play was staged in the round in the smaller theater at Zach. It's always tough and kinetic to shoot theater in the round. Unless you've been in multiple rehearsals you don't know where to actors are going to end up or just where you need to be to get a good two person grouping.
You are constantly trying to balance your need to be discreet and invisible to the actors with your need to get the images you know the marketing people need to sell the show. Of course I dress in dark colors, try not to move during emotionally charged scenes, and stay low. As cameras have evolved I've found my original way of shooting theater to still be the most compelling. That's manual focus and manual exposure.
There are no "do overs" for the photographer during the dress rehearsal. This is the last chance the cast will have to go straight through the performance before they have an audience. If I don't get what I want it's just too bad.
The only issue I have with shooting performances these days is with the color filtering of the light sources. And this will be a point of contention between lighting designers who are moulding the light to drive an emotional context and photographers who are (wrongly) trying for neutral accuracy. At some point you have to accept the lighting as it is and move on. A strongly gelled light will defy any attempt to bring the scene back to neutral color, no matter how good your PhotoShop skills are. The light is part of the artistic collaboration of theater. It's part of what I'm there to document.
Shooting dress rehearsals is incredibly good for practicing your integrative photography skills. You have to think on your feet, react, make fast decisions, understand the value of exposure compromises and anticipate action and blocking. And, you'll be doing this in the dark since the house lights are gone and all the light is on the stage. That means you better know how to use your camera blindfolded.
Just takes a little practice. Better get started now.