I've never not read my student evals. They are anonymous, but handwritten and I've graded everyone's tests. For what it's worth, I only recognize handwriting on the eval if it's one of my absolute favorite students or if it's someone I've had to put a lot of extra work in with, for whatever reason. Also, that negative thing student X said is something that other people have said and I'm definitely taking it to heart.
They are usually extremely gratifying to read, but they are mostly positive reinforcement for stuff that went well in the course. For the stuff that doesn't go well, well, usually the students don't have a specific idea why and they don't write much. Specific constructive criticism is rare.
Student Evals, in my experience, are so soft/nonspecific on criticism that they don't provide actionable evaluations of profs. The exception would be when specific comments pop up about unprofessional behavior. If a prof is acting in a sexist, bullying, or otherwise unprofessional way, the evals have a lot of power. As you can imagine, the dean can't have a situation where a prof with any hint of bad behavior in his/her evals is caught abusing students.
Otherwise, we mostly enjoy them and joke about them to one another. My wife is on a run of perfect 7s and everyone in the dept is jelly that she's the coolest.