my 2p worth - my work involves a lot of summarisation, recommendation from a user preference statement. I've been able to do this with 4o / opus, but the consistency wasn't there, which required complex prompting chains to stabilise.

What I'm seeing with Sonnet 3.5 is a night-and-day step up in consistency. The responses don't seem to be that different in capability of opus / 4o when they respond well, it just does it with rock-solid consistency. That sounds a bit dull, but it's a huge step forward for me and I suspect for others.