One of the best interviews I ever went on was a pair coding exercise. The interviewer asked me to come in for a couple hours, and we worked through a problem together. The "my time is your time" vibe was really nice. An interviewer wouldn't he able to scale that kind of interviewing technique unless they were upfront with candidates about what they'd he asked to do, and had a reasonable level of confidence that a candidate would have a reasonable shot at getting the job. I really liked it, and it demonstrated that the interviewer had thought about the interview in advance.