If they are fair and honest about this (not handing out 40 or 50 hours work and calling it 30), I think that 4 days * 8 hours per week would be pretty nice.
I did a 4 * 10 job one summer when I was a teen. It was REALLY nice to have Friday as "recovery" day before the real weekend started.
I'm not sure how my family would tolerate me being gone 4 * 10, though.
Maybe I've just been self-employed for too long. In this mode of existence, one has immense schedule flexibility and yet is always working, all at the same time, in some weirdly paradoxical way. It's a lot like the life of professors; they don't have to be in the office except when teaching or having office hours, yet they're always busy.
From the vantage point of that mode of existence, an extra day doesn't do anything for me. Nothing I'd take a pay cut for, for sure. I can take a random Wednesday off anyway if I feel like it. On the other hand, I am working at least some time every day, and some days a lot.
I guess if I think back to when I was W-2 employed my butt had to be in some cube farm at 9 AM every day, a Friday off might seem more valuable.
I did a 4 * 10 job one summer when I was a teen. It was REALLY nice to have Friday as "recovery" day before the real weekend started.
I'm not sure how my family would tolerate me being gone 4 * 10, though.