I love probing the sitz. There, I've said it. Now you know. It's good to have it off my chest.
A couple of the regional theaters here combine the first orchestra reading with the sitzprobe, so you have actors running in and out and trying this and that number, and in the meantime the band just isn't up to snuff. In the end, you get neither a good orchestra rehearsal nor good sitzprobe. This was the case with the likes of Ragtime and Assassins, which is ridiculous. There's nothing like getting a good band rehearsal in, and then probing that darn sitz. Even doing the one right after the other with a short break in between is better.