As with all such things, it depends on the company and the person doing the interview. There certainly used to be a very strong idea of "cultural fit", coupled with appearance cargo-culting, that made guessing what to wear at some places a minefield. On the one hand, if a company is putting their hiring decisions in the hands of insecure stereotype-wannabees who idolise a fantasy vision of the valley, do you want to work there anyway? On the other hand, we all need to pay the rent and sometimes if you can get past the "cultural fit" gatekeepers the rest of the company is pretty solid.
On a personal note, I always wear a suit to inteviews. I don't have many suits, but they're bespoke and tailored to fit. When I put one on, it's like a mode switch; lookin' sharp, feelin' sharp. Sometimes it's even a talking point when an interview notices (although, to be fair, at least once one interviewer appeared to have slept in his clothes and looked a complete mess, and me lookin' sharp just emphasised it). I do live and work principally in the UK, though, where wearing a shirt with buttons is not seen as dressy.
I also dress up for interviews even if the place is casual, and I even usually dress nicely for the first day of work. You’re normally introduced to 100 people on your first day, and I like to make a good impression. I’ve never had a problem with negative feedback from this. I think you can tell someone’s cultural fit better by a conversation than their clothing.
On a personal note, I always wear a suit to inteviews. I don't have many suits, but they're bespoke and tailored to fit. When I put one on, it's like a mode switch; lookin' sharp, feelin' sharp. Sometimes it's even a talking point when an interview notices (although, to be fair, at least once one interviewer appeared to have slept in his clothes and looked a complete mess, and me lookin' sharp just emphasised it). I do live and work principally in the UK, though, where wearing a shirt with buttons is not seen as dressy.