I think it depends on a few factors and is really a case-by-case situation.

I think a smaller office or workplace will appreciate the note more. Places that are constantly hiring are less likely to care. It's routine to interview cashiers at Home Depot or to do screeners at a call center. No need to write a note for that.

Older people like it. My dad gives instant points to anyone he interviews that writes (not emails--he doesn't care about that because he says email these days is meaningless) a note because he says it demonstrates actual interest and gives the impression that they are a nice person. He says lazy people won't mail a written note. For what it is worth, he interviews potential supervisors in manufacturing, where getting along with people is 79% of the job.

I personally always do a handwritten note for interviews where I feel the interviewer made an effort to get to know me as a person. Screeners? No. HR was just doing their job. 45 minute sit-down that feels like a conversation and mini-mentoring session? Thank you note. I think for this a good rule of thumb is: when they get my note in the mail, will they see my name on the card and instantly remember who I am? If yes, card.

Panels (3 or more interviewers) just get a group email if it was the kind of interview where I would normally write a note. If you spend all day there or they take you to lunch, then write each person an individual email (with content specific to them). It's unreasonable to hand write 5 thank you notes.

If they do anything to accommodate me, they get a handwritten note. This might be things like letting me interview with them at a coffee shop on the weekend or after hours, letting me do a phone interview because I live far away, or rescheduling.

As a final point, you really should mail it /'d that takes time. Bring notes with you (envelopes already stamped and filled in as much as possible) so you can mail it right away when you are done. That way they will probably get it the next day or at least within 48 hours.