I like the idea of giving candidates a choice. For me personally, I would almost always take the "homework" if it meant no (or very short) in person interview. I like to code, not interview. Still, 6-7 hours is pushing it, it should be a few hours (3 or 4 at max, if you're not going to do a face to face), and a genuinely interesting problem (the kind of problem can tell you a lot about the company itself!).

When I interviewed at Apple years ago, they gave me a take home program to solve. It was interesting and I enjoyed it a lot. It required some good algo knowledge and had to be written in C. I was told in my face to face that few people ever solve it, and I enjoyed discussing it.

But the rest of the interview was unpleasant - your typical SV brain teaser riddled, algo whiteboard sessions for 4 hours, 2 days in a row. I wasn't really expecting it and wasn't prepared (my fault), so failed miserably. I think I suffered PTSD after that for a while :).

Now I feel preparing for that sort of interview is a huge waste of my own time. It has so little relevance to reality. I'd much rather put that time into building a product or learning some new PL or whatever. At least with a coding test I'm honing skills that I'll use day to day.