Aways are a tough question and vary by specialty. I think they are not helpful for any of the ROAD specialties, including anesthesiology.
I like to refer to them as Audition rotations as you are, in effect, auditioning for a spot. Completely agree with the other posters on surgery where Audition rotations make a difference as it's a lot of hands-on auditioning that cannot easily be captured in a standard interview.
Problem is they can make or break you. Kind of like buying a stock and hoping it goes your way (no whammies plz). Could have a bad preceptor, mean co-students at the institution, etc. Or the opposite. If I was a slam dunk draft-me-in-round-1-please applicant, then I would personally avoid Audition electives. If I felt like my suturing skills were cool whip Dorito amazing, I'd consider doing the elective.